An objective of the present invention is to provide a portable information terminal device capable of exclusively storing information which is useful to identify an illegal user.If a matching degree between characteristic information extracted from a photographed image by a characteristic extraction part 402A and registered characteristic information is determined to be smaller than an authentication threshold value by a matching degree determination part, 402C, an error history information management part 404 causes an error history information storage part 414 to store error history information obtained at that time. Therefore, history information obtained when authentication has failed in the authentication process is stored as error history information only when a person who differs from a true user such as, for example, a person who has stolen a mobile phone tries to use the mobile phone illegally and characteristic information is extracted from a face image of the person, so that the person can be identified from the error history information after the mobile phone is retrieved.