The object is to reduce the contact surface pressure between the balls and
the retainer of a thrust ball bearing at slide contact positions, thereby
suppressing the wear of the retainer. By increasing the depth of drawing
of inner and outer portions embracing the balls received in pockets of
the retainer, when the balls roll on the raceways of the outer ring and
the inner ring, the balls and the retainer are adapted to slidably
contact each other at three portions, i.e. the peripheral edge of each
pocket, and the outer portion and the inner portion of the retainer.
Thus, it is possible to reduce the contact surface pressure at the
respective slide contact positions compared to the prior art. Thus, it is
possible to suppress the wear of the retainer.