To always secure stable rotation by controlling the position of a rotor on the basis of output of a displacement detecting means and changing supporting rigidity of the rotor on the basis of output of a current detecting means of a motor.

Output of a displacement sensor 3 is input to a DSP 7 through an A/D converter 6, calculation based on specified controlling characteristics is performed for specified sampling time, a magnetic bearing 4 is driven by a magnetic bearing driving circuit 8, and the position of the rotor is controlled. Current of a motor 5 is detected by a current sensor 10, and the output is input as current I to the DSP 7 through an A/D converter 11 and read for each specified sampling time. When load of the motor 5 is increased and the current I is larger than the reference current, the DSP 7 increases a gain, increases floating force of the magnetic bearing 4, improves supporting rigidity of the rotor, and stabilizes supporting. Therefore, magnetic floating force is enhanced in relation to the increase of motor load incapable of being obtained only the displacement detection, and stabilization of the rotation can be achieved.