In a developing cartridge, a first supporting member is attached to a housing and has a first developing supporting portion and a driving-force-receiving-member supporting portion. The first developing supporting portion is configured to rotatably support a first part of a rotational shaft and the driving-force-receiving-member supporting portion is configured to rotatably support a driving-force-receiving member. The second supporting member is attached to the housing and has a second developing supporting portion and a detection-rotational-body supporting portion. The second developing supporting portion is configured to rotatably support a second part of the rotational shaft and the detection-rotational-body supporting portion is configured to rotatably support a detection rotational body.