PURPOSE: To suppress the generation of nitrogen oxides by a method wherein the exhaust gas, which is discharged from the incinerator and cooled, is circulated and fed at positions higher than fire grates within the incinerator.

CONSTITUTION: In nitrogen oxides suppressing operation, primary combustion air fed from the undersides of the fire grates 2 is throttled as few as possible in order to accelerate the gasification of the refuses onto the fire grates 2 and consequently suppress the generation of nitrogen oxides. In addition, a part of the exhaust gas cooled and dust-collected in blown into the incinerator 1 through exhaust gas blowing-in nozzles 3 by means of an exhaust gas circulating ventilator 10 in order to enable to accomplish slow and complete combustion under low oxygen concentration due to the effect of the direct cooling of combustion flame, mixing and stirring of combustion gas, resulting in enabling to control the exhaust gas temperature in a predetermined range and to effectively suppress the generation of nitrogen oxide.