A compressed air energy storage and power generation method, comprising: driving an electric motor by fluctuating input power; compressing air by a compressor mechanically connected to the electric motor; storing the compressed air, which is supplied from the compressor, in an accumulator tank; driving an expander by the compressed air supplied from the accumulator tank; and generating power by a generator mechanically connected to the expander, defining, as a reference storage value, a storage value indicating that a storage amount of the air in the accumulator tank is in a predetermined intermediate state; at the reference storage value, controlling at least one of the electric motor and the generator to rotate at a rated rotation speed; when a storage value indicating a current storage amount in the accumulator tank is larger than the reference storage value, controlling at least one of the electric motor and the generator to rotate at equal to or less than the rated rotation speed; and when the storage value indicating the current storage amount in the accumulator tank is smaller than the reference storage value, controlling at least one of the electric motor and the generator to rotate at equal to or more than the rated rotation speed and equal to or less than a maximum permissible rotation speed; characterized in that if the storage value indicating the current storage amount in the accumulator tank is larger than the reference storage value, then the generator is rotated at equal to or less than the rated rotation speed so as to maintain a rated output, and if the storage value indicating the current storage amount in the accumulator tank is smaller than the reference storage value, the generator is rotated at equal to or more than the rated rotation speed and equal to or less than the maximum permissible rotation speed so as to maintain the rated output. driving an electric motor by fluctuating input power; compressing air by a compressor mechanically connected to the electric motor; storing the compressed air, which is supplied from the compressor, in an accumulator tank; driving an expander by the compressed air supplied from the accumulator tank; and generating power by a generator mechanically connected to the expander, defining, as a reference storage value, a storage value indicating that a storage amount of the air in the accumulator tank is in a predetermined intermediate state; at the reference storage value, controlling at least one of the electric motor and the generator to rotate at a rated rotation speed; when a storage value indicating a current storage amount in the accumulator tank is larger than the reference storage value, controlling at least one of the electric motor and the generator to rotate at equal to or less than the rated rotation speed; and when the storage value indicating the current storage amount in the accumulator tank is smaller than the reference storage value, controlling at least one of the electric motor and the generator to rotate at equal to or more than the rated rotation speed and equal to or less than a maximum permissible rotation speed; characterized in that if the storage value indicating the current storage amount in the accumulator tank is larger than the reference storage value, then the generator is rotated at equal to or less than the rated rotation speed so as to maintain a rated output, and if the storage value indicating the current storage amount in the accumulator tank is smaller than the reference storage value, the generator is rotated at equal to or more than the rated rotation speed and equal to or less than the maximum permissible rotation speed so as to maintain the rated output.