A CAES generator includes a plurality of motors, a plurality of compressors, a pressure accumulator, an expander, a generator, an electric-motor inverter that changes a rotation speed of each of the motors, a feed command receiver that receives input power as a feed command value before feeding the input power, and a controller. The controller includes a compressor number calculation unit that calculates a maximum number of motors that are allowed to be driven at a rating based on the feed command value, and a compressor drive control unit that drives at the rating, the motors, the number of which is the maximum number calculated by the compressor number calculation unit.