1. An iris authentication apparatus comprising: iris area extraction means for extracting iris areas from a sensed registration eyeball image and a sensed collation eyeball image; registration pattern generating means for, when said iris area extraction means extracts an iris area from the registration eyeball image, generating a registration iris pattern image by performing polar coordinate transformation of an image in the extracted iris area; collation pattern generating means for, when said iris area extraction means extracts an iris area from the collation eyeball image, generating a collation iris pattern image by performing polar coordinate transformation of an image in the extracted iris area; and collation means for collating the registration iris pattern image output from said registration pattern generating means and the collation iris pattern image output from said collation pattern generating means on the basis of a correlation therebetween.