An image generation method includes an acquisition step of acquiring a plurality of pieces of tomogram data of a subject, the plurality of pieces of tomogram data representing cross-sections at a substantially identical position of the subject； a calculation step of calculating a motion contrast by using pieces of pixel data corresponding to one another among the plurality of pieces of tomogram data that have been acquired； a comparison step of comparing the motion contrast with a threshold； a generation step of generating a motion contrast image in which a brightness corresponding to the motion contrast that is lower than the threshold is lower than a brightness corresponding to the motion contrast that is higher than the threshold； and a change step of changing the threshold.
