A variable speed pumping up generator includes a first speed control unit for outputting a rotating speed command signal for controlling a pump turbine in accordance with a power output command and outputting an excitation control signal to an AC excitation unit of the generator, and a second speed control unit for controlling, in a generation mode, an amount of AC excitation from an AC excitation unit when a rotating speed of a rotary shaft departs from a lower limit setting or an upper limit setting. The setting is set in accordance with the rotating speed generated during a normal operation.