Abstract: A carbonate spring bath system includes a supplying device of a CO.sub.2 gas, a dissolving device of the CO.sub.2 gas into a bath water, and a bathtub. The supplying device of the CO.sub.2 gas comprises a combustor for obtaining a combustion gas including the CO.sub.2 gas, a CO.sub.2 adsorption tower connected to the combustor through a gas feed line and connected to the dissolving device through a supply line, a cooler for cooling the combustion gas prior to being fed to the CO.sub.2 adsorption tower and a heater for heating an adsorbent filled in the CO.sub.2 adsorption tower for desorbing the CO.sub.2 gas therefrom. The adsorbent capable of adsorbing the CO.sub.2 gas from the combustion gas at a relatively low adsorption temperature and of desorbing the CO.sub.2 gas therefrom at a relatively high desorption temperature. As the CO.sub.2 gas in the combustion gas is adsorbed in the CO.sub.2 adsorption tower in accordance with a thermal swing adsorption method, the CO.sub.