The invention provides a gas-turbine fuel nozzle that includes a plurality of fuel supply channels to which fuel is supplied, a plurality of fuel/sweep-fluid supply channels to which fuel or a sweep fluid for sweeping the fuel is supplied, and a plurality of injection holes that are provided at downstream ends of the fuel supply channels or the fuel/sweep-fluid supply channels and that inject the fuel guided from the fuel supply channels or the fuel/sweep-fluid supply channels; a sweep-fluid supply channel that is connected to the fuel/sweep-fluid supply channels to guide the sweeping; and sweep-fluid cooling means for cooling the sweep-fluid to a temperature lower than a self-ignition temperature of the fuel.