To provide a radial ball bearing capable of preventing lubricant from leaking out of a bearing inside even for an open type bearing without a sealing member, and preventing heating due to wearing or friction, seizure of a ball, etc.

The radial ball bearing comprises an outer ring having the outer ring raceway surface, an inner ring having the inner ring raceway surface, a plurality of balls 5 disposed between the outer ring raceway surface and the inner ring raceway surface, a retainer 20 for providing the pocket 7 at a plurality of circumferential positions by forming the whole circumferentially, and rotatably retaining a plurality of the balls in the pocket. The pocket of the reatainer comprises spherical recessed parts 21, 23, and a cylindrical recessed part 22. Lubricant storage parts A, B are formed near a border between the spherical recessed part and the cylindrical recessed part, and formed to open type in which the bearing opens in an axial direction, and lubricant is sealed in the bearing.