1. A communication terminal apparatus comprising: an application execution unit operable to perform prescribed operations for communications; an address book updating unit operable to update first party information included in an address book to second party information, the address book being stored on an address book storage medium and including one or more pieces of party information and one or more names in one-to-one correspondence; and an application information updating unit operable to update a piece of party information that is stored on an application information storage medium and the same as the first party information to the second party information according to the updating by the address book updating unit, the application information storage medium storing thereon one or more pieces of party information and being referred to by the application execution unit.