Provided is a valve assembly for a gas vessel including: a valve body mounted at an inlet of the gas vessel and connected to a gas supply source; a connection part connected to the gas supply source on a side surface of the valve body; a check valve mounted on the connection part; and a safety valve mounted on the side surface of the valve body to discharge a fuel gas in the gas vessel to the outside when a gas pressure inside the gas vessel increases above a certain pressure or higher. The valve assembly for a gas vessel is connected to the lower end of the valve body and arranged in the gas vessel to block the gas passage when the fuel gas introduced through the valve body is charged to a set value to prevent overcharging of the fuel gas.