A one-way clutch is proposed which includes an outer race having a radially inner surface in which a plurality of pockets are formed. Rollers are each received in one of the pockets. Wedge-shaped spaces are defined between respective cam surfaces of the pockets and a shaft inserted through the outer race. When the shaft rotates in one direction, the rollers are wedged into the narrow ends of the respective wedge-shaped spaces, thereby locking the clutch. When the shaft rotates in the opposite direction, the rollers move toward the wide ends of the wedge-shaped spaces, thereby unlocking the clutch. The casing includes a main body and a cylindrical member fitted in the main body and made of an elastic synthetic resin. The outer race is fitted in the cylindrical member.