To provide a controller of a generator which can reduce receiving power from a commercial power system by accelerating the control of generated power.

In the controller of the generator which supplies power to a private load in cooperation with the commercial power system, when the received power falls from a reverse feeding preventing level, a speed command corresponding to a rated frequency or the speed command at the warm-up time of the generator is outputted to a governor. Thus, the controller of the generator is constituted so that the generated power can be limited at a high speed. Accordingly, the power control of higher speed than conventional control can be performed.