A belt device for an image forming apparatus, includes an endless belt; a first and second support rollers, each including a rotary shaft, that support the belt with tension; a contacted member that contacts the belt; a shaft displacement device to displace any of the rotary shafts of the support rollers; and a main rotary shaft disposed at a side of the rotary shaft of the first support roller moved by the shaft displacement device along a stretching direction of the stretched surface of the endless belt that the contacted member contacts, relative to a contact portion between the endless belt and the contacted member, and at an opposite side of the contacted member in a direction perpendicular to the stretching direction of the endless belt. As the first support roller and the second roller rotate about the main rotary shaft, the endless belt is separated from the contacted member.