PURPOSE: To obtain a stable combustion action with the moisture content in the wastes raised by selecting the wastes into fine particles and coarse particles by the selection air flow and burning the fine particles in suspension in the combustion chamber and burning the coarse particles fluidized in the fluidized layer and, at the same time, maintaining the temperature of the fluidized layer at constant temperature.

CONSTITUTION: Wastes A are supplied to the combustion chamber 2 from the supply port 4 through a feeder 1 and chute 13. Then, at first, the wastes A are selected into fine particles F and coarse particles G by the selection air flow C supplied from a selection air flow nozzle 5. Next, the fine particles F are burned in suspension in the combustion chamber 2 and, at the same time, the coarse particles that are fluidized are burned in the fluidized layer 3. The temperature of the fluidized layer 3 at this time is maintained constant by a fluidized layer temperature maintaining device 6 regardless of the rate of the coarse particles G to the fine particles F. Namely, based on the detection signal from a temperature detection device 18 provided in the fluidized layer 3 a waste distribution device 17 is controlled by a controller 19. For example, when the fine particles F are larger in volume and the temperature of the fluidized layer 3 is low, the volume of the wastes A that are supplied directly to the fluidized layer 3 from a lower supply port 16 is increased.