Patent ID: 7181688

Claim:
A document retrieval device that retrieves a document matching a retrieval condition inputted thereto, comprising: document information storage means for storing, in a table, plural documents each in association with words extracted from the document, the document having a document ID identifying a storage location in the storage means of a document file; retrieval condition acquisition means for receiving the retrieval condition that includes at least a word given by a user as a retrieval condition in combination with a logical operator; matching document retrieval means for retrieving plural documents matching the retrieval condition received by the retrieval condition acquisition means, out of the documents stored in the document information storage means and applying a specified logical operation to the result to acquire the document ID of the documents that match the retrieval condition; related word calculation means for acquiring, as related words, the words stored in the document information storage means that are associated with plural matching documents retrieved by the matching document retrieval means, and calculating, with regard to each of the related words, a degree of relatedness among the matching documents, based on an expression with variables that includes a number of the documents containing the related word among the matching documents and a number of the documents containing the related word among the documents stored in the document information storage means; related part extraction means for extracting a plurality of related parts from contents of the document, on the basis of the related word and the degree of relatedness which are acquired by the related word calculation means; and related part output means for outputting the related parts acquired by the related part extraction means and displaying them in order of appearance in the documents along with a score representing a relative degree of relatedness.