A pressing pulley is formed of a tapered roller having an angle same as a taper angle of a head pulley and having a length in a rotation axis direction of a tapered outer tube which is set to be shorter than a length in a rotation axis direction of a taper-shaped outer tube of the head pulley, and the pressing pulley is arranged in a state where a large-diameter-side end portion of the tapered outer tube is positioned in a vicinity of an outer peripheral edge portion of a fan-shaped belt and the pressing pulley is inclined so that a peripheral surface of the tapered outer tube presses a portion close to the outer periphery in a length from a pivot to the outer peripheral edge portion of the fan-shaped belt wound around the head pulley against a peripheral surface of the taper-shaped outer tube of the head pulley.