In masquerading determination processing, a masquerading determination unit reads image data representing an image of an identification target on which a striped pattern is projected from an image storage unit to extract the striped pattern appearing in a face region of the image represented by the read image data. Subsequently, the masquerading determination unit determines whether a stripe in the face region in the image is a straight line or not. When the stripe is a straight line, because the identification target is a plane object such as a photograph or an image display device so that it can be determined that the target is at least not a person himself, the masquerading determination unit determines that the target masquerades. On the other hand, unless the stripe is a straight line, because the identification target has a solid configuration having three-dimensional irregularities to have a possibility of being a person himself, the unit determines that the target might not masquerade.