Radial passages (22) that penetrate from the inner diameter side to the outer diameter side of a retainer (8) are provided between inner wall surface portions (14) of a pocket (10) facing each other in an axial direction of the retainer and a rolling element (6) so that the radial passages (22) serve as a grease reservoir as well as a grease passage for allowing the grease adhering to the rolling element (6) to move onto an outer ring raceway surface (4a). The radial passages (22) are made up of arc-shaped spaces (18) between the rolling element (6) and the inner wall surface portions (14) of the inner wall surface of a pocket (10) and segment shaped spaces (20) between the rolling element (6) and arcuate recesses (16) at the four corners of the pocket (10).