An outer retainer for a one-way clutch has a cylindrical portion and a flange portion extending radially outward from an axial end of the cylindrical portion. The flange portion has three or more arc-shaped major parts disposed circumferentially and arc-shaped minor parts, each adjacent two of the major parts being connected to one another through a minor part, the major and minor parts projecting radially outward to different extents, and the arc-shape of the major and minor parts constituting continuously the shape of the outer periphery of the flange portion.