PURPOSE: To attain high efficiency by placing priority for each servo system and applying arithmetic processing with higher priority to a servo system with high priority placed so as to use a signal processing circuit in common without deteriorating the performance of a section to be controlled such as an actuator.

CONSTITUTION: The arithmetic processing such as equalizing is applied sequentially digitally in the period of 1/4H as shown in figure (g) with respect to a fine tuning servo system by an arithmetic processing circuit 3. On the other hand, as to a coarse tuning servo system, although the arithmetic processing is applied every time timing pulses e, f are generated basically, since the response speed requested to the fine tuning servo system is faster than that of the coarse tuning servo system, the arithmetic processing of the fine tuning servo system is executed with priority as shown in figure (h). That is, the arithmetic processing of the coarse tuning servo system is executed at a time when no arithmetic processing of the fine tuning servo system is applied. The control to place the higher priority onto the arithmetic processing of the fine tuning servo system than that of the coarse servo system is executed by a controller 5.