To enable the furnace wall of a flue gas circulating wall-cooled incinerator to withstand the incineration of plastics, in order to prevent the occurrence of hazardous materials at incinerating of the plastics, etc.

The furnace wall 3 and internal furnace wall 4 of this flue gas circulating wall-cooled incinerator are cooled, by making a taken-in flue gas flow along the inside of the wall 3 or between the walls 3 and 4 or blowing the flue gas along the inside of the wall 3 or between the walls 3 and 4.