A color electrophotographic image forming apparatus, in which a plurality of cartridges each including an electrophotographic photosensitive drum are detachably mountable to a main assembly of the apparatus, includes an exposure device for forming an electrostatic latent image on the drum; a cartridge supporting member capable of demountably supporting the cartridges and movable between an inside position and an outside position; a driving device for driving the drum; an intermediary transfer belt onto which an image provided by developing the electrostatic latent image formed on the drum is transferred; and a controller for controlling execution of image formation in response to print jobs received by the apparatus. The controller causes the exposure device to expose the drum to light after completion of a last print job, and the controller stops drive of the drum by the driving device in a state that the exposed area is opposed to the intermediary transfer belt.