Lever holders (14a, 14a) are provided to a cylinder body (14) attached to a bar handle 12 and hinged portions (32c) and (33a) of a lever body (32) which is one rotation member and an interlocking member (33) which is the other rotation member are pivotally supported by the lever holders (14a and 14a). Stopper portions (32e, 33e) are disposed to protrude from the hinged portions (32c, 33a). The stopper portion (33e) of the interlocking member (33) is allowed to abut on a stopper abutting surface (14b) provided in the cylinder body (14). The stopper abutting surface (14b) is formed perpendicular to the axial line of the bar handle (12) and the side of the cylinder body opposite to the bar handle is provided integrally with a front cover wall portion (14c) which covers the abutting portion between the stopper portion 33e and the stopper abutting surface (4b).