An imaging system (10) according to the disclosure includes: a first control unit (11) configured to control, in such a way as to fix a focal position in a predetermined position, an iris imaging means for capturing an image focusing on an iris of a target person; an authentication unit (12) configured to authenticate the target person, based on an iris image of the target person being captured by the iris imaging means controlled by the first control unit (11); and a second control unit (13) configured to control the iris imaging means in such a way as to scan a focal position in a predetermined range, in order to re-authenticate the target person when authentication of the target person fails.