An ophthalmologic apparatus includes a first changing unit configured to change a size of an aperture of a diaphragm arranged in an optical path connecting a subjects eye and a light source and in a position conjugate with a pupil of the subjects eye, and a second changing unit configured to, if a signal for instructing the first changing unit to change the size of the aperture from a first size to a second size smaller than the first size is output to the first changing unit, change an amount of light of a fixation target image projected onto the subjects eye from a first light amount to a second light amount smaller than the first light amount.
