Provided is an image forming apparatus that together with being able to suppress rotation unevenness is capable of preventing unexpected downtime due to a broken belt. A guide member guides the swing of a swing gear on an arc that connects a first position where the swing gear is engaged with an idle gear, and a second position where the swing gear is not engaged with the idle gear. A transmission cutoff mechanism cuts off transmission of a drive force transmitted to a driven pulley via a belt to a driven shaft when a motor rotates in the reverse direction. A control unit, in a case where rotation unevenness meets a condition, causes the swing gear to swing to the first position by reverse rotation of the motor, which causes the drive force to be transmitted to the driven shaft.