A crown-shaped retainer (20) has: an annular base section (22); pockets (24) which penetrate through the retainer in the radial direction and which have openings (a) on one axial side of the retainer; and pairs of protrusions (26), each of the pairs of protrusions (26) being located on both circumferential side of the opening (a) of each of the pockets (24). The inner peripheral surface of each of the pockets (24) comprises: a spherical portion (28) which is located on the inner side of the retainer in the radial direction; and a circular cylindrical portion (30) which is located on the outer side of the retainer in the radial direction. The inner diameter (phi D2) of the circular cylindrical portion (30) is greater than the ball diameter (dw).