1. A composition determination device comprising: subject detection means configured to detect a subject in an image based on acquired image data; still detection means configured to detect a still state, with an image based on said image data, or a subject detected by said subject detection means, as the object thereof; and composition determination means configured to determine a composition, with only real subjects or only unreal subjects, of subjects detected by said subject detection means, as the object thereof, based on detection results of said still detection means.