To prevent oil leak and breakage of a housing by force acting on a clutch lever support supporting a clutch lever.

A bearing 14 supporting an input shaft 11 provided with a clutch 12 on a tip part thereof on an inner bulkhead 10c of a housing 10 is retained on the inner bulkhead by a front retainer 15 for preventing coming off. A clutch lever support 16 is attached on the inner bulkhead by screwing a screw part 16c projecting from the lower end surface 16a1 of a main body part 16a into the inner bulkhead through the front retainer to hold and fix the front retainer between the lower end surface 16a1 of the main body part and the inner bulkhead. A fulcrum part 17a of the clutch lever 17 is oscillatably supported by a pivot part 16b at a tip of the clutch lever support, is oscillated by applying operation force to an operation part 17c, and releases the clutch by pressing a release member 12a of the clutch by a pressing part 17b.