A developing cartridge, comprising: a housing that is configured to accommodate developing material therein and to have a first end termed left end and a second end termed right end along a predetermined direction, a from-first-to-second direction which is a right direction being defined along the predetermined direction as being directed from the first end to the second end, a from-second-to-first direction which is a left direction being defined along the predetermined direction as being directed from the second end to the first end; a developing roller having a rotational shaft that extends in the predetermined direction and that has a first part which is made up by a left end portion of the developing roller shaft and a second part which is made up by a right end portion of the developing roller shaft, the first part and the second part being apart from each other in the predetermined direction, the second part being located on a downstream side relative to the first part in the from-first-to-second direction; a driving-force-receiving member that is configured to receive driving force from an outside of the developing cartridge; a detection rotational body that is configured to be detected by a detecting unit that is provided outside of the developing cartridge; a first supporting member (51, 115) that is attached to the housing and that has a first developing supporting portion (54, 117), the first developing supporting portion (54, 117) being configured to rotatably support the first part of the rotational shaft, characterized in that the first supporting member (51, 115) further comprises a driving-force-receiving-member supporting portion (56, 123) which is configured to rotatably support the driving-force-receiving member; a second supporting member (81, 116) that is attached to the housing and that has a second developing supporting portion (84, 117) and a detection-rotational-body supporting portion (88, 124), the second developing supporting portion (84, 117) being configured to rotatably support the second part of the rotational shaft, the detection-rotational-body supporting portion (88, 124) being configured to rotatably support the detection rotational body, and in that the driving-force-receiving member and the detection rotational body are disposed on opposite side walls of the housing. a housing that is configured to accommodate developing material therein and to have a first end termed left end and a second end termed right end along a predetermined direction, a from-first-to-second direction which is a right direction being defined along the predetermined direction as being directed from the first end to the second end, a from-second-to-first direction which is a left direction being defined along the predetermined direction as being directed from the second end to the first end; a developing roller having a rotational shaft that extends in the predetermined direction and that has a first part which is made up by a left end portion of the developing roller shaft and a second part which is made up by a right end portion of the developing roller shaft, the first part and the second part being apart from each other in the predetermined direction, the second part being located on a downstream side relative to the first part in the from-first-to-second direction; a driving-force-receiving member that is configured to receive driving force from an outside of the developing cartridge; a detection rotational body that is configured to be detected by a detecting unit that is provided outside of the developing cartridge; a first supporting member (51, 115) that is attached to the housing and that has a first developing supporting portion (54, 117), the first developing supporting portion (54, 117) being configured to rotatably support the first part of the rotational shaft, characterized in that the first supporting member (51, 115) further comprises a driving-force-receiving-member supporting portion (56, 123) which is configured to rotatably support the driving-force-receiving member; a second supporting member (81, 116) that is attached to the housing and that has a second developing supporting portion (84, 117) and a detection-rotational-body supporting portion (88, 124), the second developing supporting portion (84, 117) being configured to rotatably support the second part of the rotational shaft, the detection-rotational-body supporting portion (88, 124) being configured to rotatably support the detection rotational body, and in that the driving-force-receiving member and the detection rotational body are disposed on opposite side walls of the housing.