To add dustproof performance to a retainer without providing a sealing device.

This retainer 4 is constituted of a left retaining ring 5 and a right retaining ring 5 retaining rolling bodies 3 from the left and right in the axial direction, and the respective retaining rings 5, 6 are respectively provided with annular dustproof walls 7, 8 formed into the width approximating to the space in the radial direction between an inner ring 1 and an outer ring 2 arranged with the rolling bodies 3.... A purality of rolling body retaining projections 9..., 10... are projectingly provided in the axial direction, on the respective inner walls 7a, 8a of the dustproof walls, at regular intervals in the circumferential direction, the each section is formed into a nearly T-shape, and the left and right retaining rings 5, 6 sandwichedly hold the respective rolling bodies 3..., under the condition in which respective mutually opposed rolling body holding projections 9, 10 are spaced from each other in the circumferential direction.