An angular contact ball bearing includes an outer ring having an outer ring race formed on an inner surface thereof, an inner ring having an inner ring race provided on the outer surface thereof, a plurality of rolling elements provided between the outer ring and the inner ring, an annular cage for retaining the rolling elements, and seals provided on openings between the respective ends of the inner and outer rings. The cage is made of a synthetic resin material and is supported through the guide of the rolling elements. The cage includes a plurality of cylindrical pockets arranged peripherally for retaining the rolling elements and a reduced diameter portion formed at ends of the pocket for regulating the radial movement of the cage while being in contact with the rolling element.