A gas filling apparatus having a filling nozzle with high operability. A gas filling apparatus 1, comprising; a filling mechanism for transporting a gas from a gas supply source via a gas transporting pipe while measuring flow rate of the gas; a filling hose 3 connected to the gas transporting pipe, the filling hose having a filling nozzle 4 at an end; a nozzle hook 5 on which the filling nozzle is hung; and a guide mechanism 7 for guiding the filling nozzle from the nozzle hook to a predetermined position when the filling nozzle is detached from the nozzle hook. The guide mechanism can guide the filling nozzle to a filling port of a fuel tank mounted on a vehicle, which allows the filling nozzle to move to the filling port of the fuel tank with ease even though the filling nozzle is heavy or a high pressure gas such as hydrogen gas is handled. The nozzle hook can include an injection port 5d for injecting a dry gas to the filling nozzle hung on the nozzle hook.