To automatically adjust a drift and gain of a sensor by automatically initially adjusting a magnetic bearing device by vibrating the magnetic bearing device so as to bring it into contact with a rotary body protecting bearing by reducing gain of a control means.

A reference signal and a feedback signal from a control object 24 are imparted to an adder 21 so that these are subtracted. Position detecting sensor output is used as the feedback signal from the control object 24. Output of the adder 21 is imparted to a proportional circuit 22, a proportional constant K is multiplied, and a main control circuit 23 is a driving circuit for driving respective magnetic bearings. The control object 24 is driven by the main control circuit 23. When the proportional constant K of the proportional circuit 22 is reduced, gain of a control system reduces, and control becomes unstable, so that a rotary shaft contacts with the bearings. The vibrational center is determined from a maximum value and a minimum value of the sensor output, and a difference from a present offset quantity is added or subtracted. Gain and an offset quantity are repeatedly adjusted to obtain stable rotation of the rotary shaft.