In the revolving restricted state, the planetary gear meshes with the drive input gear, and the clutch mechanism is unable to transmit the rotational drive force; in the freely revolvable state, the planetary gear is separated apart from the drive input gear, and the clutch mechanism is able to transmit the rotational drive force, the drive transmission switching mechanism is provided with first and second abutting portions which are configured to come into contact with the planetary arm rotated in the freely revolvable state so as to initialize the revolving position of the planetary gear, and the drive transmission switching mechanism is capable of selecting which one of the first and second abutting portions will come into contact with the planetary arm in accordance with the position of the drive input gear transmitting the rotational drive force among the plurality of drive input gears.