To provide a retainer for ball bearings capable of preventing occurrence of shortage or excess of lubricant, and has good ball retaining characteristics.

This retainer 10 is provided with a plurality of ball retaining pockets 20 formed along the peripheral direction on one surface of an annular body 11. The pocket 20 consists of a bottom wall 23, both side walls 22, and a pair of claws 21. Both side walls 22, and the respective inner surfaces 21a to 23a of a pair of claw pieces 21 have a larger curvature than that of a ball 30 respectively, and are formed out of spherical recessed surfaces of different types from each other. A position NP the nearest to the outer-periphery surface of the ball of inner surfaces 22a of both side walls is set around an peripheral- direction line PL passing through the center O of the ball.