An outer ring 3a is formed so as to have a large thickness and the pitch circle diameters Dp of balls 6 are shifted to the inside diameter side of the present ball bearing. The radiuses of curvature Ro, Ri of the section shapes of an outer ring raceway 2a and an inner ring raceway 4a are increased with respect to the diameter Db of the balls 6. At the same time, the diameter Db of the balls 6 and the thickness of an inner ring 5a are not set excessively small to thereby be able not only to prevent Brinell impressions from being formed in the outer ring raceway 2a but also to prevent the inner ring 5a from being damaged or cracked.