To provide a controller for making a system follow up a target track even under such a bad condition that a random disturbance is caused and physical parameters featuring dynamic characteristics are unknown.

This controller is equipped with a means 1 which estimates physical parameters of a system, a means 2 which generates a partial input for performing adaptive linear compensation for the system based on the result estimated by the means 1 and a means 3 which generates a partial input for improving robustness of the system linearized by the means 2, and the robustness of the system is improved even when the physical parameters are estimated insufficiently.