An image forming apparatus including a cleaning unit removably mountable to an apparatus main body under a state of being supported by a transfer unit, and movable with respect to the transfer unit in a longitudinal direction of a cleaning member under a state of not being mounted to the apparatus main body. The apparatus main body includes a frame unit portion configured to position a cartridge with respect to the apparatus main body in an axial direction of a photosensitive drum. The frame unit portion is configured to position the cleaning member with respect to the apparatus main body in the longitudinal direction under a state in which the transfer unit is mounted to the apparatus main body.