A disclosed gas supplying apparatus includes a pressure controller that reduces a primary pressure thereby providing a secondary pressure greater than a process pressure at which a predetermined process is performed and less than the atmospheric pressure in a secondary pipe; a pressure sensor that measures a pressure in the secondary pipe; a first open/close valve provided in the secondary pipe; an open/close valve controller that opens or closes the first open/close valve; a pressure comparator that compares the pressure measured by the pressure sensor in the secondary pipe with a first set pressure that is greater than the process pressure by a predetermined pressure; and a controller that outputs a signal to the open/close valve controller thereby closing the first open/close valve, when the pressure comparator determines that the pressure in the secondary pipe is less than the first set pressure.