Abstract: A one-way clutch comprising an outer race having at least one pocket and a stepped portion formed on an axial one end face of the outer race; an inner race spaced apart from and radially inside of the outer race and coaxially arranged for a relative rotational movement; a roller disposed in the pocket and adapted to transmit torque between the outer race and the inner race ; a cage rotatable relative to the outer race and having a window formed in a cylindrical portion and having a circumferential width smaller than a diameter of the roller and adapted to hold the roller; and a spring disposed in the pocket and adapted to bias the roller toward an engagement direction with respect to a cam surface; wherein a cover portion for covering at least a part of the pocket is provided on the other axial end face of the outer race.