A cartridge that is mountable to an apparatus main assembly of an image forming apparatus, the apparatus main assembly having mounted a photosensitive drum separate from the cartridge, the cartridge comprising: a developing roller including an elastic layer for bearing developer (t), wherein the elastic layer can be pressured against the photosensitive drum; a frame (342, 362) supporting the developing roller; a groove (342y, 362c) provided on the frame (342, 362) a movable part slidably in the groove (342y, 362c) so as to be movable to a first position and to a second position relative to the frame (342, 362); and an elastic part provided between the frame (342, 362) and the movable part to urge the movable part; wherein the movable part includes a force receiving part that receives an external force in a direction of moving from the first position to the second position, wherein, when the movable part receives the external force at the force receiving part and is at the second position, the movable part receives urging force from the elastic part, in a direction of moving the movable part from the second position to the first position, and wherein the force receiving part is suitable to receive the external force so that, in a state that the cartridge is mounted on the apparatus main assembly, the movable part is at the second position and the elastic layer is pressured against the photosensitive drum, wherein the cartridge further comprises: a drive input member for receiving input of rotational force to rotate the developing roller, wherein the developing roller is disposed at one end side of the frame (342, 362), and the force receiving part of the movable part is disposed at another end side of the frame (342, 362), with respect to a first direction parallel to a straight line connecting a rotational center of the developing roller and a rotational center of the drive input member, as viewed in a rotational axis direction of the developing roller. a developing roller including an elastic layer for bearing developer (t), wherein the elastic layer can be pressured against the photosensitive drum; a frame (342, 362) supporting the developing roller; a groove (342y, 362c) provided on the frame (342, 362) a movable part slidably in the groove (342y, 362c) so as to be movable to a first position and to a second position relative to the frame (342, 362); and an elastic part provided between the frame (342, 362) and the movable part to urge the movable part; wherein the movable part includes a force receiving part that receives an external force in a direction of moving from the first position to the second position, wherein, when the movable part receives the external force at the force receiving part and is at the second position, the movable part receives urging force from the elastic part, in a direction of moving the movable part from the second position to the first position, and wherein the force receiving part is suitable to receive the external force so that, in a state that the cartridge is mounted on the apparatus main assembly, the movable part is at the second position and the elastic layer is pressured against the photosensitive drum, wherein the cartridge further comprises: a drive input member for receiving input of rotational force to rotate the developing roller, wherein the developing roller is disposed at one end side of the frame (342, 362), and the force receiving part of the movable part is disposed at another end side of the frame (342, 362), with respect to a first direction parallel to a straight line connecting a rotational center of the developing roller and a rotational center of the drive input member, as viewed in a rotational axis direction of the developing roller. a drive input member for receiving input of rotational force to rotate the developing roller, wherein the developing roller is disposed at one end side of the frame (342, 362), and the force receiving part of the movable part is disposed at another end side of the frame (342, 362), with respect to a first direction parallel to a straight line connecting a rotational center of the developing roller and a rotational center of the drive input member, as viewed in a rotational axis direction of the developing roller.