Provided is high-performance H.sub..infin. control technology suitable for position control or speed control of semiconductor exposure apparatus, servo writer of hard disk, etc. A series compensator in the classical control technology represented by the PID compensator is employed as a frequency weight of loop shaping, whereby the design technology in the conventional classical control can be succeeded to and a high-performance control system can be realized even for cases where there is an oscillation mode of a controlled object to become a problem on control performance in the servo band, which was difficult to realize by the classical control technology. Also, using a robust stabilizing compensator obtained from a generalized plant having constant matrix weights, a high-performance control system can be realized even for cases where there is an oscillation mode of the controlled object to become a problem on control performance in the servo band, which was difficult to realize by the conventional classical control technology.