1. An iris registration method, comprising: a first step of capturing, by a capture device, a plurality of iris images at different pupil diameter/iris diameter ratios of an iris of a person to be registered and storing the plurality of iris images in a computer-readable recording medium; a second step of acquiring aggregation of iris images by performing at least one of duplication and deletion of at least one iris image of the plurality of iris images in the computer-readable recording medium so that distribution of the number of iris images with respect to the pupil diameter/iris diameter ratio is uniform; and a third step of obtaining, while evaluating authentication performance, a predetermined number of registration features from the aggregation of the iris images which is obtained in the second step and storing the predetermined number of registration features in a computer-readable recording medium.