To provide a robust and stable servo control system even when a servo valve which adjusts working oil supplied from a hydraulic pressure source to an actuator has a modeling error.

This servocontrol system adjust the working oil supplied from the hydraulic pressure source 1 to a hydraulic cylinder 3 by the servo valve 2 and controls the operation on the steering surface 4 of an aircraft operated by this hydraulic cylinder 3 by a controller 6 equipped with a compensator 14 which outputs a manipulated variable so that the controlled variable of the steering surface 4 matches a target value. In this case, the compensator 14 is designed by robust control technology so that the compensator is robust and stable against a modeling error of the servo valve 2 in addition to variation in the natural vibration frequency of the system consisting of the steering surface 4 and hydraulic cylinder 3.