A combustor of the prior art that defines the outlet position and direction of an air hole and suppresses adhesion of flame to an air hole outlet can reduce a discharge amount of NOx by increasing a distance over which fuel and air are mixed with each other. However, such a combustor is not sufficiently discussed for measures to suppress the occurrence of combustion oscillation resulting from the variation of a flame surface.A combustor 2 according to the present invention includes a combustion chamber 5 to which fuel and air are supplied; air holes 32 adapted to supply air to the combustion chamber 5; fuel nozzles 25 adapted to supply gaseous fuel to the air holes 32; and orifices 24 adapted to allow the gaseous fuel supplied to the air holes 32 to cause a pressure drop.