A nozzle assembly for injecting fuel and compressed air into a combustion chamber of a gas turbine combustor is provided. The nozzle assembly includes a nozzle body disposed in the combustor and having a coolant outlet on one end of which an inside of the nozzle body communicates with the combustion chamber, a spray nozzle disposed in the nozzle body and including a plurality of first nozzle tubes each having a first flow path formed therein to allow combustion air to flow into the combustion chamber and a fuel hole formed to supply fuel, and a second nozzle tube having through-holes to allow the first nozzle tubes to pass therethrough and a second flow path formed to supply fuel, and a diaphragm disposed inside of the nozzle body and including a plurality of coolant flow holes through which a coolant supplied to the nozzle body is supplied towards one end of the nozzle body and a plurality of tube holes through which the first nozzle tubes pass.