A personal authentication system comprises an imaging section for capturing an image of a user's eye including the iris; pupil/iris region extraction section for extracting a pupil region and an iris region from the captured image; a three-dimensional polar coordinate image creation section for estimating the three-dimensional center position of the eyeball based on the extracted pupil region and iris region and for creating a three-dimensional polar coordinate image by converting the iris region into three-dimensional coordinates with reference to the center position of the eyeball; and a three-dimensional polar coordinate image coding section for creating a three-dimensional polar coordinate image code formed by extracting and coding a characteristic of the created three-dimensional polar coordinate image. The personal authentication system can create iris information highly accurately representing characteristics of a user's iris independent of the direction of line of sight of the user.