To discriminate a telephone number of high frequency in use, from/to which a telephone set user receives/originates calls frequently, to automatically register this telephone number in a telephone book without user's setting registration of the telephone number.

A telephone terminal 10 includes; a display means 12 for displaying prescribed information; an input means 13 for accepting various operation inputs such as a telephone number; and a call originating/terminating means 11 for performing call processing in response to being informed of call originating telephone number information for call origination of the telephone terminal 10 or call terminating telephone number information for call termination of the telephone terminal 10. The telephone terminal 10 includes a means which generates a table for arranging many pairs of data each of which consists of identifiers associated with the call originating telephone number information for call origination or the call terminating telephone number information for call termination of the telephone terminal 10 and a service duration of call connection, and discriminates whether the call originating telephone number information or call terminating telephone number information has a high frequency in call origination or termination or not on the basis of data in the table and adds an index number corresponding to the operation input means to store it in the table as a telephone book registration number.