A belt member is rotatably extended around a plurality of rotatable members of an image forming apparatus for forming a toner image on a recording material by using a developer containing a magnetic carrier. The belt member includes a layer, formed of a crystalline resin material, having an outer peripheral surface and an inner peripheral surface. The layer has a hardness of 0.25 GPa or more and 0.40 GPa or less at the outer peripheral surface and a hardness of 0.10 GPa or more and 0.20 GPa or less at the inner peripheral surface.