A nozzle, a combustor, and a gas turbine, which are capable of atomizing fuel efficiently, are provided. A fuel injection device for the combustor may include a plurality of guide channels connected to a pilot fuel passage through which fuel is supplied, an injection chamber connected to the plurality of guide channels, the fuel being merged in the injection chamber, and an injection hole formed at a tip of the injection chamber to inject the fuel, and the injection chamber may include a decompression space to drop a pressure therein.