An image processing device includes a first identification unit configured to identify the spatial configuration of a vessel in an object to be imaged, a second identification unit configured to identify information on a blood flow rate of the vessel based on an SLO moving image obtained by signal light that has a focus position deeper than at least a part of the area of the vessel, and an acquisition unit configured to acquire information on a blood flow of the vessel based on the identified area and the information on the blood flow rate.