We introduce a method for inspecting the function of the respiratory circuit of an anesthesia machine using "Valve Checker" devised by a manufacturer. With this method, the function of an inspiratory valve can be confirmed by the pressure not being removed when pressure is applied by connecting the "Valve Checker" directly with the inspiratory opening. Additionally, the function of an expiratory valve can be confirmed by the pressure being removed and also by the deflated bag being inflated when pressure is applied by connecting the "Valve Checker" directly with an expiratory opening. This is a method whereby a delicate cushioning of pressure by a hose is excluded and the function of the inspiratory valve and expiratory valve can be inspected independently and easily.