An image forming apparatus including: guide portions provided in strips on opposite ends of an inner circumferential surface of an endless belt; a driving roller supporting the endless belt; a driven roller supporting the endless belt; first restriction members having first contact surfaces which come into contact with the guide portions when the endless belt moves in a belt width direction; and second restriction members having second contact surfaces which come into contact with the guide portions when the endless belt moves in the belt width direction, the second contact surfaces are placed nearer to a center in the belt width direction than the first contact surfaces, and an angle between the first contact surfaces and the inner circumferential surface in the belt width direction is larger than an angle between the second contact surfaces and the inner circumferential surface in the belt width direction.