A combustor is provided that can ensure combustion stability even when operated on low BTU gas without needing any equipment for preventing back-flow of fuel gas during operation on pilot fuel. The combustor includes a first perforated plate disposed upstream of a combustion chamber, the first plate having a plurality of nozzle holes and air holes; a second perforated plate disposed on the upstream side of the first plate; and a plurality of gas nozzles each of which is inserted into corresponding nozzle holes. The gas nozzle has a leading end located inside the corresponding one of the nozzle holes. Each of the gas nozzles includes a jet hole portion having a diameter smaller than that of a gas jet hole of the gas nozzle; and a passage portion designed to form an air passage on the outer circumference of the leading end portion of the gas nozzle.