In one embodiment, a carbon dioxide capturing system includes an absorber to absorb CO2 from first gas into lean liquid, and produce rich liquid that is the lean liquid absorbing the CO2 and second gas that is the first gas removing the CO2, and a regenerator to separate third gas including the CO2 from the rich liquid flowing from the absorber, and provide the lean liquid and the third gas. The system further includes a flowmeter to measure a flow rate of the third gas, a liquid level gauge to measure a liquid level of the lean liquid and/or the rich liquid, and a controller to regulate a quantity of heat energy supplied to the regenerator based on the flow rate of the third gas, and regulate a total amount of the lean liquid and the rich liquid in the system based on the liquid level.