A gas inspection method includes: inputting a signal for opening a secondary valve; measuring, by a secondary pressure gauge, a pressure P on a downstream side of an orifice of a flow rate controller at a time point when a period t elapses from the input of the signal for opening the secondary valve; measuring, by the secondary pressure gauge, a standard deviation σ of the pressure P on the downstream side of the orifice of the flow rate controller at the time point when the period t elapses from the input of the signal for opening the secondary valve; and determining whether or not an open degree of the secondary valve is normal by comparing the pressure P and the standard deviation σ of the pressure P with a threshold value P0 of the pressure and a threshold value σ0 of the standard deviation of the pressure.