A compressed air energy storage and power generation method comprising: a first air compression step of driving a first compressor by fluctuating input power to compress air; a first air storage step of storing the air, compressed by the first compressor, in a first pressure accumulation tank (12; 71A, 71B,..., 71N); a first air supply step of supplying the compressed air from the first pressure accumulation tank to a first expander ; a first power generation step of driving a first generator by the first expander to generate power; a first heat exchange step of performing heat exchange, in a first heat exchanger , between the air compressed by the first compressor and a heat medium to heat the heat medium; a heat medium storage step of storing the heat medium, heated in the first heat exchanger, in a heat medium tank ; a second heat exchange step of performing heat exchange, in a second heat exchanger , between the compressed air supplied from the first pressure accumulation tank and the heat medium supplied from the heat medium tank to heat the compressed air; an air discharge step of, when the amount of compressed air stored in the first pressure accumulation tank has exceeded a predefined amount during the first air storage step, discharging the air compressed by the first compressor to an outside without storing the compressed air in the first pressure accumulation tank; and wherein in the air discharge step, the air compressed by the first compressor is heat-exchanged in the first heat exchanger with the heat medium to heat the heat medium, and the compressed air is subsequently discharged to the outside without introducing the compressed air into the first pressure accumulation tank. a first air compression step of driving a first compressor by fluctuating input power to compress air; a first air storage step of storing the air, compressed by the first compressor, in a first pressure accumulation tank (12; 71A, 71B,..., 71N); a first air supply step of supplying the compressed air from the first pressure accumulation tank to a first expander ; a first power generation step of driving a first generator by the first expander to generate power; a first heat exchange step of performing heat exchange, in a first heat exchanger , between the air compressed by the first compressor and a heat medium to heat the heat medium; a heat medium storage step of storing the heat medium, heated in the first heat exchanger, in a heat medium tank ; a second heat exchange step of performing heat exchange, in a second heat exchanger , between the compressed air supplied from the first pressure accumulation tank and the heat medium supplied from the heat medium tank to heat the compressed air; an air discharge step of, when the amount of compressed air stored in the first pressure accumulation tank has exceeded a predefined amount during the first air storage step, discharging the air compressed by the first compressor to an outside without storing the compressed air in the first pressure accumulation tank; and wherein in the air discharge step, the air compressed by the first compressor is heat-exchanged in the first heat exchanger with the heat medium to heat the heat medium, and the compressed air is subsequently discharged to the outside without introducing the compressed air into the first pressure accumulation tank. <EOS>