A roughness of an outer ring raceway surface 14 formed on an inner peripheral surface of an outer ring 13 is made larger than a roughness of inner ring raceway surfaces 12a, 12b of an inner ring 11. Also, an average roughness Ra of the outer ring raceway surface 14 is set within 0.1 .mu.m.ltoreq.Ra.ltoreq.0.5 .mu.m in an axial direction and a circumferential direction in ranges of b.sub.1/(B/2).ltoreq.0.9, b.sub.2/ (B/2).ltoreq.0.9 and in a measured length of 0.1 mm to 1.0 mm where B is a width of the outer ring 13 and b.sub.1, b.sub.2 are a distance from both end surfaces of the outer ring 13 in the axial direction respectively. A roughness parameter S of the outer ring raceway surface is set within 0