A developing cartridge having a first side plate and a second side plate spaced opposite from the first side plate, a developer carrying member rotatably supported between the side plates, a developer supplying member rotatably supported between the side plates, a input member to which driving force is input rotatably supported by the first side plate, a primary developing gear to which the driving force is transferred provided on the developer carrying member at the first side plate, a secondary developing gear to which the driving force is transferred provided on the developer carrying member at the second side plate, and a supply gear to which the driving force is transferred provided on the developer supplying member at the second side plate, wherein the input member and the supply gear are arranged so that their projections in the direction of the rotation axis of the developer supplying member overlap.