PURPOSE: To recover inorganic waste without change of properties by burning combustible waste by heating it from a lower part of a rotary furnace, blowing cold air from a separate position, and controlling to maintain a temperature in the furnace at a temperature or lower of change of properties of the waste.

CONSTITUTION: A combustion burner and a cold air diffuser are so alternately arranged at a bottom side separated from a position directly under an axial center of a rotary furnace 5 as to form a combustion zone B in the furnace 5 at an intermediate position of an incinerator box 9. A regulator receives a signal from a thermocouple 40 arranged at an inlet of each suction tube 7a of an exhaust duct 7, and inputs an operation signal to a driver of a damper 30 for regulating an air flow rate of a cold air diffuser 23. In this case, cold air diffusing amount is regulated by a damper 39 to control to maintain a temperature of the zone B in the furnace 5 at a temperature or lower of change of properties of inorganic waste.