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 in which distribution of the number of iris images with different pupil diameter/iris diameter ratios is uniform by classifying the plurality of iris images previously stored in the computer-readable recording medium in the first step into classes according to the pupil diameter/iris diameter ratios, setting target numbers of iris images for the classes respectively, duplicating an iris image in a first class of the classes when a current number of iris images in the first class is less than the target number of the first class, and deleting an iris image in a second class of the classes when a current number of iris images in the second class is greater than the target number of the second class; 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, wherein the second step and the third step are embodied as computer executable instructions and are executed by a processor.