A bearing sleeve 8 is press-fitted into a housing 7, and an axial portion 2a of an axial member 2 is inserted into the inner peripheral surface 8a of the bearing sleeve 8, and then a thrust member 10 is attached to the lower end of the inner peripheral surface 7c of the housing 7 and positioned in a predetermined position to fix it by ultrasonic welding. The lower end of the housing 7 is pressed against the outer peripheral surface of the thrust member 10 with applying ultrasonic vibration, to fix the melting junction surface of the housing 7 on the thrust member 10.