1. An iris recognition method, which uses a camera, microprocessor, iris enrollment database and iris recognition program and considers pupil size variations due to changes in intensity of lighting so as to enhance iris recognition accuracy, comprising: obtaining multiple iris images having different pupil sizes by capturing iris images of a person to be enrolled with a camera while adjusting brightness of lighting so that the pupil size of the person to be enrolled varies from a maximum size to a minimum size; storing the obtained iris images and associated iris size information for enrollment in the iris enrollment database interworking with an iris recognition device; capturing an iris image for identification of a person to be identified with a camera installed in the iris recognition device; selecting enrolled iris images of each enrolled person from the iris enrollment database on the basis of iris size information of the iris image captured for identification, and measuring similarity between the iris image captured for identification and the selected enrolled iris images through comparison; and performing authentication or identification of the person to be identified on the basis of results of similarity measurement between the captured iris image and the selected enrolled iris images.