An assembly for a ball bearing with double raceway assembled in an outer ring member provided with double row raceway surfaces apart from each other in an axial direction from one side in an axial direction, on an inner peripheral surface includes an inner ring member provided with double raceway surfaces apart from each other in an axial direction in correspondence to the double raceway surfaces on an outer peripheral surface, double row cages arranged in respective outer diameter sides of the double raceway surfaces of the inner ring member, and a plurality of ball rows respectively held by the double rows cages. The inner ring member is set to be non-separable from the respective cages and the respective ball rows, and can be assembled in the outer ring member from one side in the axial direction.