In a state in which a first ball 103 is assembled in between a first inner peripheral raceway surface of an outer ring 105 and an outer peripheral raceway surface of a shaft 101, and a second ball 104 is placed in between a second inner peripheral raceway surface of the outer ring 105 and an outer peripheral surface of the shaft 101, a first distance "a" from a plane "q" generally perpendicular to a central axis "p" of the shaft 101 to the second ball 104 and a second distance "b" from the plane "q" to a stepped portion 107 of the shaft 101 are measured. Then, the size in the axial direction of the inner ring 102 is adjusted on the basis of a difference between the first distance "a" and the second distance "b".