A developing cartridge which is detachably mountable in an apparatus main body of an image forming apparatus, the developing cartridge comprising: a housing including a first side wall and a second side wall which are provided to oppose each other, the housing configured to accommodate developer therein; a receiving member provided on an outer side of the first side wall to be rotatable about a first axis which extends in an opposing direction of the first side wall and the second side wall, the receiving member configured to couple with a driving force output member provided in the apparatus main body to receive a driving force from the driving force output member; a developing roller held between the first side wall and the second side wall to be rotatable about a second axis which extends in parallel to the first axis with a space therebetween, the developing roller configured to rotate by the driving force received by the receiving member; a detectable rotary member provided on the outer side of the first side wall to be rotatable about a third axis which extends in parallel to the first axis with a space therebetween, and including a first detectable portion and a second detectable portion which is provided away from the first detectable portion in a rotational direction about the third axis, the detectable rotary member configured to rotate by the driving force received by the receiving member from a first rotational position where the first detectable portion is detected by a detection member provided in the apparatus main body to a second rotational position where the second detectable portion is detected by the detection member; and a cut-off mechanism configured to cut off a transmission of the driving force from the receiving member to the detectable rotary member, characterized in that the cut-off mechanism is configured to cut off the transmission in a state where the detectable rotary member is positioned in the second rotational position. a housing including a first side wall and a second side wall which are provided to oppose each other, the housing configured to accommodate developer therein; a receiving member provided on an outer side of the first side wall to be rotatable about a first axis which extends in an opposing direction of the first side wall and the second side wall, the receiving member configured to couple with a driving force output member provided in the apparatus main body to receive a driving force from the driving force output member; a developing roller held between the first side wall and the second side wall to be rotatable about a second axis which extends in parallel to the first axis with a space therebetween, the developing roller configured to rotate by the driving force received by the receiving member; a detectable rotary member provided on the outer side of the first side wall to be rotatable about a third axis which extends in parallel to the first axis with a space therebetween, and including a first detectable portion and a second detectable portion which is provided away from the first detectable portion in a rotational direction about the third axis, the detectable rotary member configured to rotate by the driving force received by the receiving member from a first rotational position where the first detectable portion is detected by a detection member provided in the apparatus main body to a second rotational position where the second detectable portion is detected by the detection member; and a cut-off mechanism configured to cut off a transmission of the driving force from the receiving member to the detectable rotary member, characterized in that the cut-off mechanism is configured to cut off the transmission in a state where the detectable rotary member is positioned in the second rotational position.