A process cartridge includes a photosensitive cartridge and a developing cartridge. The developing cartridge includes a developing roller, an input gear, a transmission gear, and a supporting cover. The input gear includes a contact portion, an outer circumferential wall, and a gear portion. The contact portion is in contact with a coupling member to receive the driving force. The outer circumferential wall and the gear portion rotate about a rotational axis defining an axial direction when the contact portion receives the driving force. The outer circumferential wall has a curved surface whose center of radius of a curvature is coincident with the rotational axis. The transmission gear is meshingly engaged with the gear portion to transmit the driving force from the input gear to the developing roller. The supporting cover covers the curved surface of the outer circumferential wall to rotatably support the outer circumferential wall.