A process cartridge that is configured to be detachably mounted in an apparatus main body of an image forming apparatus, the process cartridge comprising: a drum cartridge comprising a photosensitive drum; and a developing cartridge configured to be movably attached to the drum cartridge, the developing cartridge comprising: a developing roller configured to face and contact the photosensitive drum, the developing roller configured to be connected to or disconnected from the photosensitive drum by a spacing member provided on the apparatus main body, by moving the developing cartridge relative to the drum cartridge along a connecting or disconnecting direction; a bearing member (57, 58) for holding a rotational shaft of the developing roller; and a developing drive input member into which a driving force for rotating the developing roller is inputted; wherein the drum cartridge has an abutment portion (35, 42) with which the bearing member (57, 58) is brought into abutment by virtue of a rotational moment acting about the developing drive input member when the driving force is inputted into the developing drive input member, characterized in that a straight line, which is perpendicular to the rotational axis of the developing drive input member and which connects the abutment portion (35, 42) with a rotational axis of the developing drive input member, extends substantially in the same direction as said connecting or disconnecting direction of the developing roller to or from the photosensitive drum. a drum cartridge comprising a photosensitive drum; and a developing cartridge configured to be movably attached to the drum cartridge, the developing cartridge comprising: a developing roller configured to face and contact the photosensitive drum, the developing roller configured to be connected to or disconnected from the photosensitive drum by a spacing member provided on the apparatus main body, by moving the developing cartridge relative to the drum cartridge along a connecting or disconnecting direction; a bearing member (57, 58) for holding a rotational shaft of the developing roller; and a developing drive input member into which a driving force for rotating the developing roller is inputted; a developing roller configured to face and contact the photosensitive drum, the developing roller configured to be connected to or disconnected from the photosensitive drum by a spacing member provided on the apparatus main body, by moving the developing cartridge relative to the drum cartridge along a connecting or disconnecting direction; a bearing member (57, 58) for holding a rotational shaft of the developing roller; and a developing drive input member into which a driving force for rotating the developing roller is inputted; wherein the drum cartridge has an abutment portion (35, 42) with which the bearing member (57, 58) is brought into abutment by virtue of a rotational moment acting about the developing drive input member when the driving force is inputted into the developing drive input member, characterized in that a straight line, which is perpendicular to the rotational axis of the developing drive input member and which connects the abutment portion (35, 42) with a rotational axis of the developing drive input member, extends substantially in the same direction as said connecting or disconnecting direction of the developing roller to or from the photosensitive drum.