PURPOSE: To slip a clutch before slipping of a belt by providing a retractor spring whose outer peripheral edge is fixed to the inner edge of a pressure plate and inner peripheral edge is fixed to the actuating piston, reducing diameter of an actuating piston, and directly cooling the clutch with oil.

CONSTITUTION: A starting clutch 10 has a clutch housing 25, a following shaft 11 for driving a hub 15, an actuating piston 18 provided for the hub, a diaphragm spring 52, a pressure plate 45, and an endplate 38, and a clutch plate 78 adhered to a sleeve shaft 74. A retractor spring 64 is provided whose outer peripheral edge 65 is engaged with the inside edge 47 of the pressure plate and inner peripheral edge 66 is fixed to the actuating piston 18. Oil is supplied to the clutch plate 78 from an oil opening 82. Due to the retractor spring 64, the diameter of the piston becomes smaller than that of the clutch, and the clutch functions as a fuse for slipping of a belt. In addition, oil is cooled sufficiently.