To rapidly perform a compensating processing when a fault occurs in each system.

The respective kinds of position feedback of the two redundant systems are defined as the stroke burdens L1, L2 of motors 2, 3 in the respective systems, and also defined as the integrated values Ef1, Ef2 of rotation detectors in the respective systems. The position detecting result of a whole stroke L in the redundant actuator 1 is fetched from a potentiometer 4, and defined as the value Ef. The fetched value Ef is compared with the integrated values Ef1, Ef2 of the systems, so as to obtain ratios Gc1, Gc2. The ratios Gc1, Gc2 are multiplied by a position command value Ec with respect to the whole stroke L of the redundant actuator 1. One product is defined as the position command value Ec1 to the one motor 2, and the other product is as the position command value Ec2 to the other motor 3.