Disclosed is a cartridge attachable/detachable to/from an apparatus body of an image forming apparatus. A bearing member for pivotally supports a rotation member has an engaged portion that is arranged at a part on one end side of the cartridge in a direction of a rotational axis of the rotation member and engaged with an engaging portion provided in the apparatus body. An engagement state between the engaged portion and the engaging portion is maintained until at least a coupling of the rotation member is coupled to a driving shaft provided in the apparatus body in a process of attaching the cartridge to the apparatus body. A movement of the bearing member to at least the other end side in the direction of the rotational axis with respect to the apparatus body is restricted when the engaged portion and the engaging portion are put into the engagement state.