A combustor reduces combustion vibration and the generation of nitrogen oxides and includes a burner to mix fuel with compressed air and to eject the mixture; a liner that is coupled to one end of the burner and forms a combustion chamber in which the fuel-air mixture is combusted to produce high-pressure gas; a transition piece to receive a flow of the high-pressure gas from the liner and to discharge the high-pressure gas to a turbine; a plurality of resonance modules disposed on an outer circumferential surface of the liner at positions spaced apart from each other along a circumferential direction of the liner; and a fuel supply unit coupled to each of the plurality of resonance modules and configured to supply fuel to each of the plurality of resonance modules. The resonance modules may be disposed on an outer circumferential surface of the transition piece instead of the liner.