A gas separation/extraction apparatus comprises a tank for separating and extracting a specific gas element from a gas mixture, the tank containing an adsorbent for adsorbing the gas element from the gas mixture, a pump having a cylinder and a piston housed therein, the pump being adapted to alternately pressurize and decompress the inside of the tank as the piston reciprocates, a first three-way solenoid valve connected between an exhaust port of the tank and a suction port of the pump, a second three-way solenoid valve connected between a discharge port of the pump and the suction port of the tank, and a pressure balance unit connected between the second three-way solenoid valve and a suction port of the tank, and adapted gradually to eliminate a difference in pressure between the tank and the pump as the tank is switched from a decompressed state to a pressurized state.