An adaptive optics (AO) optical system is used, to perform accurate alignment between the AO optical system and a subject's eye. An ophthalmologic apparatus according to the present invention includes a positional relationship change unit (e.g., a driving mechanism including a stage for moving the apparatus) configured to change a positional relationship between a subject's eye and an optical system including an aberration measurement unit (e.g., a Shack-Hartmann wavefront sensor) in a first irradiation state of the subject's eye with measurement light, and an irradiation state change unit (e.g., a mechanism for changing an irradiation position) configured to change an irradiation state of the subject's eye with the measurement light from the first irradiation state to a second irradiation state for correcting an aberration of the subject's eye based on a measurement result of the aberration measurement unit.
