An electrophotographic image forming apparatus includes a main assembly; a cartridge including process means actable on an electrophotographic photosensitive member, the process cartridge being detachably mountable relative to the main assembly; an opening, provided in the main assembly of the apparatus, for permitting mounting and demounting of the cartridge; an openable member, provided in the main assembly of the apparatus, for openably closing the opening; an exposure device, provided on the openable member, for exposing the electrophotographic photosensitive member; the cartridge including a first unit, and a second unit pivotably connected with the first unit; a first positioning portion provided in the main assembly of the apparatus, wherein the exposure device is provided with a second positioning portion for positioning between the exposure device and the second unit of the cartridge by engagement with the cartridge by closing the openable member.