A control method for supplying an inert gas from an inert gas source to a storage container for a molten metal through a gas feed path provided with a flow sensor for monitoring the gas flow rate and a solenoid valve for opening and closing the gas feed path for use with metal molding. The control method includes steps of turning off the solenoid valve if a temperature of the storage container is lower than a preset temperature, and turning off the flow sensor; otherwise turning on the solenoid valve and turning on the flow sensor; and stopping the output of the heater of the storage container when the gas flow rate is lower than the preset amount; these steps are controlled in accordance with a command signal from a controller.