1. An image processing device comprising: one or more processors configured to: compare a substantially spherical photographic subject such that, among a plurality of captured images including the photographic subject, an image as a processing target and another image as a comparison target are compared using each of the plurality of captured images as the processing target, and detect a motion vector of a whole three-dimensional spherical model with respect to the processing target; perform motion compensation on the processing target, based on the detected motion vector of each of the plurality of captured images; and synthesize each of the captured images that are obtained as a result of the motion compensation.