1. An image generation apparatus comprising: a grip unit adapted to grip a target object; an image capturing unit adapted to capture an image of at least one of the target object and said grip unit; a control unit adapted to control an orientation of said grip unit; a first image obtaining unit adapted to obtain an image obtained by causing said image capturing unit to capture said grip unit controlled by said control unit so as to place the target object in one predetermined orientation of a plurality of predetermined orientations with respect to said image capturing unit and the target object in the one predetermined orientation as a grip-state image corresponding to the one predetermined orientation; a second image obtaining unit adapted to obtain, as a non-grip-state image corresponding to the one predetermined orientation, an image of said grip unit that does not grip the target object and is placed in a predetermined orientation coincident with the orientation controlled to place the target object in the one predetermined orientation; and an image generation unit adapted to generate a target object image including only the target object for the one predetermined orientation based on a difference between the grip-state image and the non-grip-state image corresponding to the one predetermined orientation.