An electrophotographic image forming apparatus detachably mounts a process cartridge including an electrophotographic photosensitive drum and includes a frame having an opening; a door movable between closing and opening positions; a cartridge-carrying tray movable among a latent image formation position, a mounting and demounting position, and a movable position therebetween; and a regulating member movable between a regulating position for regulating movement of the door from the opening position to the position when the tray is beyond the movable position, and a permitting position for permitting movement of the door from the opening position to the closing position when the tray is at the movable position.