In an iris image pickup method in which an image signal picking up an iris is allowed to pass through a high-pass filter (41L) and a lens position in which an output of the high-pass filter (41L) indicates a peak value is searched by a mountaineering method, thereby capturing an iris image focused on the iris, when an amount of a high luminance component included in the image signal is equal to or greater than a predetermined value, a peak position of a high frequency component in the image signal passing through a narrow-band high-pass filter (41H) for causing only a high band in a pass band of the high-pass filter (41L) to pass therethrough is obtained by searching for a whole area within a predetermined range in place of a search for a focusing position by the mountaineering method, and is set to be an iris focusing position. Consequently, it is possible to acquire a clear iris image having a high authentication rate which is focused on the iris in place of glasses. Also in the case in which an authentication object person wears the glasses, consequently, an image focused on the iris can be acquired.