Abstract: A a body-site image obtained by capturing an image of a body site of a user is acquired. On the basis of the acquired body-site image, the orientation of the body site within the body-site image is detected. A template pattern conforming with the detected orientation is extracted from a template-pattern storage unit storing a plurality of template patterns. The acquired body-site image is converted into a body-site pattern obtained by extracting characteristic information from the body-site image. Authentication of the user is performed by comparing the body-site pattern obtained as a result of the converting and the extracted template pattern, thereby allowing appropriate personal authentication to be performed even when the orientation of a hand held over an imaging apparatus and the orientation of the imaging apparatus in registering vein data are different from those in performing authentication.