To improve the influx property of a lubricant into a raceway groove and the retainability of the lubricant in the raceway groove.

Chamfering portions 23, 23 are provided in a boundary portion (region circled with ) between each raceway groove 22, 22 and the inner peripheral faces 24a, 24a of shoulder portions 24, 24, respectively, in a non- contact side of the side face portions of an outer ring 20, and chamfering portions 33, 33 are provided in a boundary portion (region circled with ) between each of raceway grooves 32, 32 and the outer peripheral face 34a of a shoulder portion 34, respectively, in a non-contact side to the center portion of an inner ring 30.