A pair of rim portions (4a) and (4b) is formed in the shape of a discontinuous segmental circular ring, which includes cutout portions (8a) and (8b), respectively, at one position. The cutout portions of the respective rim portions are concentrically disposed so as to face each other with a predetermined interval therebetween in an axial direction while having the same phase in a circumferential direction. A plurality of pillar portions (6) form pockets (10) where rollers (14) are retained. An expandable elastic connecting portion (12), which connects one end portion (84a) of one rim portion in the circumferential direction to the other end portion (82b) of the other rim portion in the circumferential direction, is provided at the pair of rim portions.