A design method of an output feedback control system is proposed on the basis of an improved optimal regulator technique and application of the method to an electrical drive system is presented. The control system structure of the output feedback control system is clarified by comparing it with that of the full state variable feedback control system synthesized by the improved optimal regulator technique. Difference action as well as proportional and integral actions are included in the controller of the output feedback control system, on the other hand, only proportional action and integral action are introduced in the controller of the full state feedback control system. Low static sensitivity for variations of the parameters of the controlled object is attained, and the compensating action for the input delay times due to the processing time required to execute the employed control algorithm with the microprocessor are also taken into account.