An image forming apparatus is swung with a stopper which is swingable simultaneously with a switching member, and which allows rotation of an output gear by being disengaged from the output gear with a swinging movement of the switching member to an ON side, and which stops the rotation of the output gear by being engaged with the output gear with a swinging movement of the switching member to an OFF side. When the switching member is swung to the OFF side, the stopper is engaged with the output gear at the same time as the switching member is disengaged from the triggering member or before the switching member is disengaged from the triggering member. Accordingly, a descent of a pressing plate at the time of stopping the pressing plate is prevented without using a one-way clutch.