An image forming apparatus, comprising: an apparatus main body to which a cartridge can be detachably mounted; a drive force transmission member arranged to transmit drive force to a drive force receiving member of the cartridge; and a control unit arranged to perform a rotation control operation, where rotation of the drive force transmission member is controlled, wherein image formation is performed on recording material by performing forward rotation of the drive force transmission member and transmitting drive force to the drive force receiving member of the cartridge, wherein the drive force transmission member includes a plurality of first engaging portions wherein the drive force receiving member is configured to rotate forwards when the drive force transmission member rotates forwards in a state where the plurality of first engaging portions engage with a plurality of second engaging portions that the drive force receiving member has, and image formation on the recording material can be performed while the drive force receiving member is being rotated forwards, wherein, of the plurality of first engaging portions and the plurality of second engaging portions, one plurality of engaging portions each at least move in a radial direction centered on a rotation axis line of the drive force transmission member, and can move between an engageable position where the other plurality of engaging portions can be engaged, and a non-engageable position where the other plurality of engaging portions cannot be engaged, wherein, the control unit is configured to execute, after the cartridge has been mounted to the apparatus main body but before image formation is performed on the recording material, (i) a forward rotation step where the drive force transmission member is rotated forwards by α° and the drive force receiving member is rotated forwards, and (ii) a backward rotation step where the drive force transmission member is rotated backwards by β°, after the forward rotation step, and wherein each of the plurality of first engaging portions is in a state disposed upstream in the forward rotation direction of the drive force transmission member from the second engaging portion out of the plurality of second engaging portions with which engaging will be realized in the end, due to the control unit having executed the forward rotation step and the backward rotation step, characterized in that α° and β° satisfy the following Expressions and α ° ≥ 360 ° / N β ° < 360 ° / N where N represents a count of the one plurality of engaging portions. an apparatus main body to which a cartridge can be detachably mounted; a drive force transmission member arranged to transmit drive force to a drive force receiving member of the cartridge; and a control unit arranged to perform a rotation control operation, where rotation of the drive force transmission member is controlled, wherein image formation is performed on recording material by performing forward rotation of the drive force transmission member and transmitting drive force to the drive force receiving member of the cartridge, wherein the drive force transmission member includes a plurality of first engaging portions wherein the drive force receiving member is configured to rotate forwards when the drive force transmission member rotates forwards in a state where the plurality of first engaging portions engage with a plurality of second engaging portions that the drive force receiving member has, and image formation on the recording material can be performed while the drive force receiving member is being rotated forwards, wherein, of the plurality of first engaging portions and the plurality of second engaging portions, one plurality of engaging portions each at least move in a radial direction centered on a rotation axis line of the drive force transmission member, and can move between an engageable position where the other plurality of engaging portions can be engaged, and a non-engageable position where the other plurality of engaging portions cannot be engaged, wherein, the control unit is configured to execute, after the cartridge has been mounted to the apparatus main body but before image formation is performed on the recording material, (i) a forward rotation step where the drive force transmission member is rotated forwards by α° and the drive force receiving member is rotated forwards, and (ii) a backward rotation step where the drive force transmission member is rotated backwards by β°, after the forward rotation step, (i) a forward rotation step where the drive force transmission member is rotated forwards by α° and the drive force receiving member is rotated forwards, and (ii) a backward rotation step where the drive force transmission member is rotated backwards by β°, after the forward rotation step, and wherein each of the plurality of first engaging portions is in a state disposed upstream in the forward rotation direction of the drive force transmission member from the second engaging portion out of the plurality of second engaging portions with which engaging will be realized in the end, due to the control unit having executed the forward rotation step and the backward rotation step, characterized in that α° and β° satisfy the following Expressions and α ° ≥ 360 ° / N β ° < 360 ° / N where N represents a count of the one plurality of engaging portions.