A region of an iris image where eyelash and other part images are mixed is identified with accuracy. The noise region of an iris image contained in a digital eye image (P1) where, for example, eyelash and eyelid parts are mixed is identified with accuracy based on characteristic curves obtained by scanning the iris image with arcs (AR1) and (AR2). Then, authentication is performed using data created based on the iris image from which the noise region is excluded. In this way, the subject can be authenticated with accuracy without being affected by noise.
