1. An image processing apparatus comprising: a motion detection unit detecting a motion of a subject to be evaluated by using an image of the subject to be evaluated; a correlation calculation unit calculating a temporal change correlation between motion amounts of a plurality of portions of the subject to be evaluated, by using a motion vector indicating the motion of the subject to be evaluated, which is detected by the motion detection unit; and an evaluation value calculation unit calculating an evaluation value to evaluate cooperativity of the motion of the subject to be evaluated by using the correlation calculated by the correlation calculation unit.