A belt driving apparatus includes a movable belt member, a stretching member configured to stretch the belt member, and a steering unit configured to stretch the belt member and to be inclined to steer the belt member in a widthwise direction substantially perpendicular to a direction of moving of the belt member. The light-guiding cover, for guiding light beams emitted by at least one light-emitting diode, has a light-guiding portion and a light output portion. The first inner wire layer includes, in the circumferential direction, an alternating sequence of copper wires and wires having higher tensile strength, arranged over the central core wire, and the second outer wire layer, and any further outer wire layer, is composed exclusively of copper wires.