Each of a cross sectional shape of a contacting portion of a stopper arm and a cross sectional shape of an outer peripheral surface of a pedal shaft is formed in a circular shape, wherein a curvature radius is equal to each other. Each of a cross sectional shape of a stopper surface of a supporting body and a cross sectional shape of an inner peripheral surface of a bearing portion is formed in a circular shape, wherein a curvature radius is equal to each other. A distance between a center of a first virtual circle formed by the contacting portion and a center axis of the pedal shaft is made to be equal to a distance between a center of a second virtual circle formed by the stopper surface and a center axis of the bearing portion. An angle of the stopper arm with respect to the supporting body is not changed, even when the center axis of the pedal shaft is displaced with respect to center axis of the bearing portion.