PURPOSE: To provide the controller which prevents unreasonable stress from being applied to the stationary blade varying mechanism applied for air capacity and pressure control over a fan, a compressor, etc.

CONSTITUTION: This controller consists of a master controller 10, a slave controller 11, a difference detector 14, and a decision circuit 15; and a position command signal of a servomotor which is inputted to the master controller 10 is passed through a position compensating amplifier 8 and a speed compensating amplifier 7 to become a current command signal 7b, which is inputted to the master controller 10, slave controller 11, and current compensating amplifiers 6 and 6a to supply nearly equal currents to the servomotors 1 and 1a. Thus, a force applied to the stationary blade varying mechanism is made equal to prevent an unreasonable force from operating on the mechanism.