Abstract: A one-way clutch is provided with a retainer formed with a holding hole for holding a sprag biting between an outer race and an inner race. The retainer further has a sprag restraining piece intervening between the outer race and the inner race. The sprag restraining piece protrudes radially outwardly of the retainer and resiliently bears against the sprag so that the sprag is held between the holding hole and the sprag restraining piece and urged in a direction to bite between the outer race and the inner race. The retainer serves to hold the sprag in the holding hole and also serves to prevent the sprag from coming off the holding hole by the sprag restraining piece and causes the sprag to bite between the outer race and the inner race. Portions of the retainer serve multiple roles when compared to prior retainers and, therefore, the number of parts of the one-way clutch is decreased and the structure thereof becomes simple and the assembly thereof is simplified.