A manual providing method of an electronic apparatus, the method comprising: providing (S 110) a display device with one of a plurality of manuals for an external device, wherein the plurality of manuals includes a general manual, a detailed manual, and a simple manual; obtaining a user response comprising user voice information for the provided manual, wherein the user voice information includes voice information uttered while listening to or viewing the provided manual; determining an understanding level for the provided manual based on analyzing a frequency of the voice information of the obtained user response to determine a voice height, wherein the understanding level is one of: a high level, based on the voice height of the user voice information being greater than or equal to a predetermined first value, a low level, based on the voice height of the user voice information being less than the first predetermined value and less than a predetermined second value, and a neutral level, based on the voice height of the user voice information being less than the first predetermined value and greater than or equal to the predetermined second value; substituting the provided manual with another manual among the plurality of manuals according to the understanding level, wherein the substituting the provided manual with another manual comprises: substituting the manual with the detailed manual when the understanding level is the low level and the manual corresponds to the general manual, and substituting the manual with the general manual or the detailed manual when the understanding level is the low level and the manual corresponds to the simple manual. providing (S 110) a display device with one of a plurality of manuals for an external device, wherein the plurality of manuals includes a general manual, a detailed manual, and a simple manual; obtaining a user response comprising user voice information for the provided manual, wherein the user voice information includes voice information uttered while listening to or viewing the provided manual; determining an understanding level for the provided manual based on analyzing a frequency of the voice information of the obtained user response to determine a voice height, wherein the understanding level is one of: a high level, based on the voice height of the user voice information being greater than or equal to a predetermined first value, a low level, based on the voice height of the user voice information being less than the first predetermined value and less than a predetermined second value, and a neutral level, based on the voice height of the user voice information being less than the first predetermined value and greater than or equal to the predetermined second value; substituting the provided manual with another manual among the plurality of manuals according to the understanding level, wherein the substituting the provided manual with another manual comprises: substituting the manual with the detailed manual when the understanding level is the low level and the manual corresponds to the general manual, and substituting the manual with the general manual or the detailed manual when the understanding level is the low level and the manual corresponds to the simple manual. a high level, based on the voice height of the user voice information being greater than or equal to a predetermined first value, a low level, based on the voice height of the user voice information being less than the first predetermined value and less than a predetermined second value, and a neutral level, based on the voice height of the user voice information being less than the first predetermined value and greater than or equal to the predetermined second value; substituting the provided manual with another manual among the plurality of manuals according to the understanding level, wherein the substituting the provided manual with another manual comprises: substituting the manual with the detailed manual when the understanding level is the low level and the manual corresponds to the general manual, and substituting the manual with the general manual or the detailed manual when the understanding level is the low level and the manual corresponds to the simple manual. substituting the manual with the detailed manual when the understanding level is the low level and the manual corresponds to the general manual, and substituting the manual with the general manual or the detailed manual when the understanding level is the low level and the manual corresponds to the simple manual.