A retainer includes two annular retaining plates combined with each other, and each having semispherical bulging portions arranged at predetermined intervals along a circumferential direction of the retainer. The semispherical bulging portions, which face each other, form a pocket having a ring-like shape, for retaining a ball. The pocket includes a ball non-contact portion formed in a ball facing surface of the pocket at a center portion in a pocket axial direction, the ball non-contact portion being defined by a recess extending in a pocket circumferential direction. The following relationship is set: A/(B+C)=0.70 to 0.90, where “A” represents a pocket circumferential length of the ball non-contact portion, “B” represents a diameter of the ball, and “C” represents a gap formed between the ball and the ball facing surface of the pocket.