To provide a compact radial ball bearing having stabilized turning performance at a low cost.

A curvature radius r1 of a part positioned in a circumferential side surface of each elastic piece 8 and 8 forming a pocket 9b is set a little larger than a curvature radius of a rolling surface of a ball held in the pocket 9b. A curvature radius r2 of a part positioned in an axial directional one surface of a rim part 7 in the residual part of the inner surface of the pocket 9b is set at 1.1 times or more of the curvature radius r1 of the described one part. The center of curvature of the residual part of the inner surface exists at a position displaced from the center of curvature of the one part of the inner surface, separating from the rim part 7 in the axial direction. With this structure, an increase of axial directional dimension over the whole of the holder 6 is restricted, and cross sectional area of the rim part 7 is secured. The rim part 7 is thereby formed hard to be deformed by twisting to realize the described purpose.