SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 20-F/A

o

REGISTRATION STATEMENT PURSUANT TO SECTION 12(B) OR 12(G) OF THE SECURITIES EXCHANGE ACT OF 1934

OR

x

ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended March 31, 2004

OR

o

TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from to

Commission file number:  1-5238

Nihon Densan Kabushiki Kaisha

(Exact name of registrant as specified in its charter)

NIDEC CORPORATION

(Translation of Registrants name into English)

|Japan                                           | 338 Kuzetonoshiro-cho,
Minami-ku, Kyoto 601-8205 Japan
|----------------------------------------------- | ------------------------------------------------------
|(Jurisdiction of incorporation or organization) | (Address of principal executive offices)              

Securities registered or to be registered pursuant to Section 12(b) of the Act:

|Title of Each Class | Name of Each Exchange On Which Registered
|------------------- | -----------------------------------------
|                    |                                          
|Common Stock*       | New York Stock Exchange                  

Securities registered or to be registered pursuant to Section 12(g) of the Act:

None

(Title of Class)

Securities for which there is a reporting obligation pursuant to Section 15(d) of the Act:

None

(Title of Class)

Indicate the number of outstanding shares of each of the issuers classes of capital or common stock as of the close of the period covered by the annual report.

As of March 31, 2004, 65,003,538 shares of common stock were outstanding, including 1,158,400 shares represented by 1,158,400 American Depositary Shares.

Indicate by check mark whether the registrant:  (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.  
Yes x   No o

Indicate by check mark which financial statement item the registrant has elected to follow:

Item 17  o   Item 18x



*

Not for trading, but only in connection with the listing of the American Depositary Shares, each representing one share of Common Stock.





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Nidec Corporation hereby amends its annual report on Form 20-F filed with the Securities and Exchange Commission on July 26, 2004, to file an additional exhibit as Exhibit 15.1.  This amendment is filed for the purpose of updating Item 15.  Controls and Procedures and Item 19.  Exhibits.

PART II

Item 1.

Controls and Procedures.

Management carried out an evaluation, with the participation of the Chief Executive Officer and the Chief Financial Officer, of the effectiveness of our disclosure controls and procedures as of March 31, 2004 pursuant to Exchange Act rules. Based upon that evaluation, the Chief Executive Officer and the Chief Financial Officer concluded that our disclosure controls and procedures were effective as of March 31, 2004.

Management also carried out an evaluation, with the participation of the Chief Executive Officer and the Chief Financial Officer, of changes in our internal control over financial reporting during the year ended March 31, 2004.  Based upon that evaluation, there was no change that occurred during the fiscal year ended March 31, 2004 that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting.

PART III

Item 1.

Exhibits.

|Exhibit Number | Description                                                                                                                                                                                                                                 
|-------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|1.1            | Articles of Incorporation of Nidec Corporation (English translation) ***                                                                                                                                                                    
|1.2            | Share Handling Regulations of Nidec Corporation (English translation) ***                                                                                                                                                                   
|1.3            | Regulations of the Board of Directors of Nidec Corporation (English translation) ***                                                                                                                                                        
|1.4            | Regulations of the Board of Corporate Auditors of Nidec Corporation (English translation) ***                                                                                                                                               
|2.1            | Specimen common stock certificates of Nidec Corporation (English translation)*                                                                                                                                                              
|2.2            | Form of Deposit Agreement among Nidec Corporation, Morgan Guaranty Trust Company of New York as Depositary and all owners and holders from time to time of American Depositary Receipts, including the form of American Depositary Receipt**
|4.1            | Share Exchange Agreement between Nidec Corporation and Nidec-Shimpo Corporation, dated April 25, 2003                                                                                                                                       
|8.1            | Subsidiaries of Nidec Corporation ***                                                                                                                                                                                                       
|11.1           | Code of Ethics ***                                                                                                                                                                                                                          
|12.1           | Certification of the Chief Executive Officer required by Rule 13a-14(a)                                                                                                                                                                     
|12.2           | Certification of the Chief Financial Officer required by Rule 13a-14(a)                                                                                                                                                                     
|13.1           | Certification of the Chief Executive Officer required by Rule 13a-14(b) and Section 1350 of Chapter 63 of Title 18 of the United States Code                                                                                                
|13.2           | Certification of the Chief Financial Officer required by Rule 13a-14(b) and Section 1350 of Chapter 63 of Title 18 of the United States Code                                                                                                
|15.1           | Consent of Independent Registered Public Accounting Firm                                                                                                                                                                                    

We have not included as exhibits certain instruments with respect to our long-term debt, the amount of debt authorized under each of which does not exceed 10% of our total assets, and we agree to furnish a copy of any such instrument to the Securities and Exchange Commission upon request.

___________________

*

Incorporated by reference to Nidecs annual report on Form 20-F for the year ended March 31, 2002 filed on July 5, 2002.

**

Incorporated by reference to the Registration Statement on Form F-6 (file no. 333-13894) filed on September 7, 2001.

***

Incorporated by reference to Nidecs annual report on Form 20-F for the year ended March 31, 2004 filed on July 26, 2004.



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SIGNATURES

The registrant hereby certifies that it meets all of the requirements for filing on Form 20-F/A and that it has duly caused and authorized the undersigned to sign this annual report on its behalf.

|                         |  |  | NIDEC CORPORATION |                                           
|------------------------ |  |  | ----------------- | ------------------------------------------
|                         |  |  | By                | :  Name:   /s/ Shigenobu Nagamori         
|                         |  |  | Name              | :   Shigenobu Nagamori                    
|                         |  |  | Title             | :   President, Chief Executive Officer and
|                         |  |  |                   | Representative Director                   
|                         |  |  |                   |                                           
|Date: September 10, 2004 |  |  |                   |                                           

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Exhibit 12.1

CERTIFICATION

I, Shigenobu Nagamori, certify that:

1.

I have reviewed this annual report on Form 20-F as amended by this Form 20-F/A of Nidec Corporation;

2.

Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.

Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the company as of, and for, the periods presented in this annual report;

4.

The company's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the company and have:

a)

designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the company, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this annual report is being prepared;

b)

[omitted in accordance with the guidance of SEC Release No. 33-8238] ;

c)

evaluated the effectiveness of the companys disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d)

disclosed in this report any change in the companys internal control over financial reporting that occurred during the period covered by the annual report that has materially affected, or is reasonably likely to materially affect, the companys internal control over financial reporting.

5.

The company's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the company's auditors and the audit committee of company's board of directors (or persons performing the equivalent function):

a)

all significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the company's ability to record, process, summarize and report financial information; and

b)

any fraud, whether or not material, that involves management or other employees who have a significant role in the company's internal control over financial reporting.

Date:  September 10, 2004

/s/   Shigenobu NagamoriShigenobu Nagamori
      President, Chief Executive Officer and Representative Director




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Exhibit 12.2

CERTIFICATION

I, Yasunobu Toriyama, certify that:

1.

I have reviewed this annual report on Form 20-F as amended by this Form 20-F/A of Nidec Corporation;

2.

Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.

Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the company as of, and for, the periods presented in this annual report;

4.

The company's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the company and have:

a)

designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the company, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this annual report is being prepared;

b)

[omitted in accordance with the guidance of SEC Release No. 33-8238] ;

c)

evaluated the effectiveness of the companys disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d)

disclosed in this report any change in the companys internal control over financial reporting that occurred during the period covered by the annual report that has materially affected, or is reasonably likely to materially affect, the companys internal control over financial reporting.

5.

The company's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the company's auditors and the audit committee of company's board of directors (or persons performing the equivalent function):

a)

all significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the company's ability to record, process, summarize and report financial information; and

b)

any fraud, whether or not material, that involves management or other employees who have a significant role in the company's internal control over financial reporting.

Date:  September 10, 2004

/s/  Yasunobu ToriyamaYasunobu Toriyama
      Executive Vice President, Chief Financial and Accounting Officer and Director




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Exhibit 13.1

CERTIFICATION

Pursuant to 18 U.S.C. § 1350, the undersigned officer of Nidec Corporation (the Company) hereby certifies, to such officers knowledge, that the Companys annual report on Form 20-F for the year ended March 31, 2004 as amended by this Form 20-F/A (the Report) fully complies with the requirements of Section 13(a) or 15(d), as applicable, of the Securities Exchange Act of 1934 and that the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated:  September 10, 2004



/s/   Shibenobu NagamoriShigenobu Nagamori
      President, Chief Executive Officer and Representative Director




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Exhibit 13.2

CERTIFICATION

Pursuant to 18 U.S.C. § 1350, the undersigned officer of Nidec Corporation (the Company) hereby certifies, to such officers knowledge, that the Companys annual report on Form 20-F for the year ended March 31, 2004 as amended by this Form 20-F/A (the Report) fully complies with the requirements of Section 13(a) or 15(d), as applicable, of the Securities Exchange Act of 1934 and that the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated:  September 10, 2004



/s/  Yasunobu ToriyamaYasunobu Toriyama
      Executive Vice President, Chief Financial and Accounting Officer and Director




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Exhibit 15.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration Statement on Form S-8 (File No. 333-116982) of our report dated June 8, 2004, relating to the financial statements and financial statement schedule of NIDEC Corporation, which appears in NIDEC Corporations annual report on Form 20-F for the year ended March 31, 2004.



/s/   ChuoAoyama PricewaterhouseCoopers

Kyoto, Japan

September 10, 2004





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INDEX OF EXHIBITS

|Exhibit Number | Description                                                                                                                                                                                                                                 
|-------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|1.1            | Articles of Incorporation of Nidec Corporation (English translation) ***                                                                                                                                                                    
|1.2            | Share Handling Regulations of Nidec Corporation (English translation) ***                                                                                                                                                                   
|1.3            | Regulations of the Board of Directors of Nidec Corporation (English translation) ***                                                                                                                                                        
|1.4            | Regulations of the Board of Corporate Auditors of Nidec Corporation (English translation) ***                                                                                                                                               
|2.1            | Specimen common stock certificates of Nidec Corporation (English translation)*                                                                                                                                                              
|2.2            | Form of Deposit Agreement among Nidec Corporation, Morgan Guaranty Trust Company of New York as Depositary and all owners and holders from time to time of American Depositary Receipts, including the form of American Depositary Receipt**
|4.1            | Share Exchange Agreement between Nidec Corporation and Nidec-Shimpo Corporation, dated April 25, 2003                                                                                                                                       
|8.1            | Subsidiaries of Nidec Corporation ***                                                                                                                                                                                                       
|11.1           | Code of Ethics ***                                                                                                                                                                                                                          
|12.1           | Certification of the Chief Executive Officer required by Rule 13a-14(a)                                                                                                                                                                     
|12.2           | Certification of the Chief Financial Officer required by Rule 13a-14(a)                                                                                                                                                                     
|13.1           | Certification of the Chief Executive Officer required by Rule 13a-14(b) and Section 1350 of Chapter 63 of Title 18 of the United States Code                                                                                                
|13.2           | Certification of the Chief Financial Officer required by Rule 13a-14(b) and Section 1350 of Chapter 63 of Title 18 of the United States Code                                                                                                
|15.1           | Consent of Independent Registered Public Accounting Firm                                                                                                                                                                                    

_____________________

*

Incorporated by reference to Nidecs annual report on Form 20-F for the year ended March 31, 2002 filed on July 5, 2002.

**

Incorporated by reference to the Registration Statement on Form F-6 (file no. 333-13894) filed on September 7, 2001.

***

Incorporated by reference to Nidecs annual report on Form 20-F for the year ended March 31, 2004 filed on July 26, 2004.