An image forming apparatus includes at least one supporting roller, a movable belt supported by the supporting roller, and a shifting restricting unit to prevent the movable belt from shifting to any one side along an axial direction of the supporting roller. The shifting restricting unit includes a guide rail formed between the movable belt and the supporting roller to guide movement of one end of the movable belt, and a belt pressurizing member formed at the other end of the movable belt to generate tension on the movable belt to compensate for a shifting force on the guide rail side by the guide rail.