The image projection apparatus is disclosed to which plural interchangeable optical units are selectively attachable. The apparatus includes a shift mechanism moving an attached optical unit, which is one of the plural interchangeable optical units that is attached to the apparatus, with respect to a light modulation element in a direction orthogonal to an optical axis, an actuator driving the shift mechanism, and a controller controlling drive of the actuator using a control parameter for moving the attached optical unit by a specific movement amount via the shift mechanism. The controller acquires information on at least one of a weight and an optical characteristic of the attached optical unit from a memory provided in one of the apparatus and the attached optical unit, and to change the control parameter using the acquired information.