A method for automatically opening or closing a gas barrel valve, includes: loading and aligning a gas barrel in a cabinet; separating an end cap from the gas barrel; screw-coupling a connector holder to a gas spray nozzle, from which the ends cap has been removed; winding a spring around a first shaft by enabling forward rotation of the first shaft while suppressing reverse rotation of the first shaft, which is installed in a valve handle holder so as to idle; opening a valve by enabling reverse rotation of a valve handle of the gas barrel while preventing forward rotation of the valve handle holder; and automatically closing the valve at the time of replacement of the gas barrel or when a gas leak is detected.