PURPOSE: To reduce generation amount of CO and dioxine group by a method wherein refuse is decomposed and gasified in a sand bed and generated unburnt gas is effectively burned in a combustion chamber.

CONSTITUTION: Refuse is incinerated in a sand bed and ash is produced. The burned ash undergoes melting treatment in a melting furnace 9. Cooling air is supplied into an exhaust gas duct 9b of the melting furnace 9 to cool down melting exhaust gas, and the heated cooling air is sent through the exhaust gas duct 9b to a combustion air feed nozzle 1a through which secondary air is supplied to a combustion chamber of a furnace body 1. As a result, unburnt combustion gas is prevented from being cooled in the combustion chamber, and the unburnt gas and the secondary combustion air are well mixed together.