A system configuration can evaluate the stability of an output from a user's control system including all effects of unknown dynamic characteristics and disturbances and can guarantee the stability of the output from the user's control system irrespective of the unknown dynamic characteristics and the disturbances. The control system is provided with a virtual power monitor and is thereby provided with a function of evaluation and analyzing the stability of an object to be controlled, and is such that in a user's control system the user's controlled object is controlled by the user's control strategy. Included is a conservative control strategy which receives a feedback signal from the user's controlled object and can input a control input to the user's controlled object; and a virtual power monitor which monitors power virtually transmitted from the conservative control strategy to the user's controlled object, and can evaluate the stability of an output from the user's control system.