An image forming apparatus includes a unit including at least two rotary members, and an apparatus main body configured to detachably mount the unit. The apparatus main body includes a first rotation drive source, drive rotary members corresponding to the at least two rotary members and engaging with the at least two rotary members, directly or indirectly, to rotate the at least two rotary members, respectively, and a drive force transmission mechanism transmitting a drive force of the first rotation drive source to the drive rotary members.