A starting clutch includes a clutch inner that is secured to and supported by a drive plate boss fitted to a crankshaft near the end thereof. A one-way clutch is fitted to the outer periphery of the cylindrical portion extending inwardly. A clutch outer forms an annular portion that covers the outer periphery of the drive plate. A hollow disk portion covers the inner surface and is rotatably supported by the crankshaft. The one-way clutch is clamped by the inner peripheral edge of the hollow disk portion of the clutch outer from the outer peripheral side in cooperation with the cylindrical portion of the drive plate boss, and the inner peripheral edge of the hollow disk portion of the clutch outer abuts against a flange portion of the drive plate boss extending along the inner surface of the drive plate in the centrifugal direction thereof.