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 at an opposite side of the detectable rotary member relative to the first detectable portion, 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 at an opposite side of the detectable rotary member relative to the first detectable portion, 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.