To provide a spindle motor which can be mounted on a thin large- capacity drive by improving the deflection accuracy and nonrepetitive deflection accuracy of a shaft or hub base required of a spindle motor, when the capacity of the drive is increased, and by reducing the thickness of the motor.

Two radial ball bearings 20 and 21 having different inside diameters are separately held by means of a housing 13 fixed to a printed wiring board 11, and the part of a hub base 2 is brought into contact with the inside and end face of the inner race 14 of the bearing 20. Therefore, a thin high-accuracy spindle motor can be provided, because the thickness of the span of the hub base 2 holding the shaft 1 can be increased in the axial direction and good perpendicularity can be secured between the shaft 1 and hub base 2, even if the thickness of the spindle motor is reduced.