Interlace noises of the image of an iris included in the image of an eye picked up through an interlaced scheme are corrected precisely within a short time. An image processing apparatus (30) corrects a digital image P based on only low-brightness pixels configuring the image of a pupil included in the digital image P of an eye. Accordingly, interlace noises included in the image of the pupil of the eye and that of the iris can be corrected precisely within a short time. Next, a checking apparatus (50) performs authentication on a subject person based on the image of the iris specified based on the corrected digital image P. Hence, precise authentication is enabled.