A process cartridge detachably mountable to an image forming apparatus includes, a drum; a process device actable on the drum; a cartridge frame supporting these elements; a cartridge guide; and a cartridge coupling member. The apparatus includes an opening through which the cartridge is mounted and demounted; an opening and closing member for opening and closing the opening; a main assembly side guide for supporting the cartridge guide and movable in interrelation with the opening and closing member; a main assembly coupling member, for connection with the cartridge coupling member to transmit a driving force to the cartridge coupling member; and a driving connector for effecting connection and disconnection between the main assembly coupling member and the cartridge coupling member by moving the main assembly coupling member in a direction substantially perpendicular to a cartridge mounting direction in interrelation with opening and closing of the opening and closing member.