A compressed-air storage and power generation method according to the present invention is provided with: a first air-compression step; a first air-storage step; a first air-supply step; a first power-generation step; a first heat-exchange step; a heat-medium storage step; a second heat-exchange step; and an air-discharge step. In the air-discharge step, when the amount of compressed air stored in a pressure-accumulation tank (12) exceeds a prescribed amount in the first air-storage step, the air compressed by a first compressor (10) is discharged outside without being stored in the pressure-accumulation tank (12). Therefore, it is possible to provide a compressed-air storage and power generation method by which fluctuating electrical power can be smoothed efficiently even after compressed air is stored up to the storage capacity of the storage space.