At a plurality of points in the circumferential direction of a cylindrical portion (77c), notches (90) recessed farther to the race (76a) side, in the axial direction, than the distal edge of the cylindrical portion (77c) are formed. At a part of each notch (90) closer to the race (76a) than the bottom edge thereof, a protrusion is provided protruding farther to the side opposite to the race (76a) than the cylindrical portion (77b) in the radial direction. Each protrusion serves as a latching portion (91) for locking the race in order to prevent the race (74c) from slipping out of the partner member to which the race (74c) is attached. Consequently, a structure which can ensure durability in such a state that the rigidity is low at a part for backing up the race (74c) and can reduce the manufacturing cost is attained.