A gas solution supply device comprising: a first gas-liquid separator in which gas solution is stored; a second gas-liquid separator which is provided at a stage subsequent to the first gas-liquid separator and in which gas solution to be supplied to a use point is stored; an intermediate line provided between the first gas-liquid separator and the second gas-liquid separator; a pressure booster pump that is provided on the intermediate line and is configured to increase a pressure of gas solution being supplied from the first gas-liquid separator to the second gas-liquid separator; a gas supply line that is configured to supply gas as a material of the gas solution; a gas dissolving unit that is provided on the intermediate line and is configured to dissolve the gas supplied from the gas supply line in the gas solution supplied from the first gas-liquid separator; characterized by a first valve provided on a liquid supply line that is configured to supply liquid as a material of the gas solution; a second valve provided on a gas solution supply line that is configured to supply the gas solution to the use point; a third valve provided on an exhaust line from the first gas-liquid separator to an exhaust port; a fourth valve provided on a drain line branching from the exhaust line; and a control unit that is configured to perform open and close control of the first valve, the second valve, the third valve, and the fourth valve, wherein the control unit is configured to: when the gas solution is to be supplied to the use point, perform control to open the first valve, the second valve and the third valve and close the fourth valve, and when the first gas-liquid separator and the second gas-liquid separator are to be cleaned, perform control to close the second valve and the third valve and open the first valve and the fourth valve. a first gas-liquid separator in which gas solution is stored; a second gas-liquid separator which is provided at a stage subsequent to the first gas-liquid separator and in which gas solution to be supplied to a use point is stored; an intermediate line provided between the first gas-liquid separator and the second gas-liquid separator; a pressure booster pump that is provided on the intermediate line and is configured to increase a pressure of gas solution being supplied from the first gas-liquid separator to the second gas-liquid separator; a gas supply line that is configured to supply gas as a material of the gas solution; a gas dissolving unit that is provided on the intermediate line and is configured to dissolve the gas supplied from the gas supply line in the gas solution supplied from the first gas-liquid separator; characterized by a first valve provided on a liquid supply line that is configured to supply liquid as a material of the gas solution; a second valve provided on a gas solution supply line that is configured to supply the gas solution to the use point; a third valve provided on an exhaust line from the first gas-liquid separator to an exhaust port; a fourth valve provided on a drain line branching from the exhaust line; and a control unit that is configured to perform open and close control of the first valve, the second valve, the third valve, and the fourth valve, wherein the control unit is configured to: when the gas solution is to be supplied to the use point, perform control to open the first valve, the second valve and the third valve and close the fourth valve, and when the first gas-liquid separator and the second gas-liquid separator are to be cleaned, perform control to close the second valve and the third valve and open the first valve and the fourth valve. when the gas solution is to be supplied to the use point, perform control to open the first valve, the second valve and the third valve and close the fourth valve, and when the first gas-liquid separator and the second gas-liquid separator are to be cleaned, perform control to close the second valve and the third valve and open the first valve and the fourth valve.