There is provided a method of incinerating a waste material to process incineration residues produced in a gasification furnace easily with existing equipment. A combustible gas generated when a waste material A is dry-distilled in a gasification furnace 1 is introduced into a combustion furnace 3 and combusted therein. The combustible gas is generated in the gasification furnace 1 in order to keep the temperature in the combustion furnace 3 at a temperature capable of melting incineration residues. The incineration residues are charged into the combustion furnace 3 while the combustible gas is being combusted therein, and melted into a melted material B that is discharged from an outlet 3 of the combustion furnace 3 into a receptacle 33 in which the melted material B is solidified. Air supplied to an air jacket 6 and oxygen supplied to the gasification furnace 1 and the combustion furnace 3 are heated by a heat exchange with waste gases from the combustion furnace 3. The heat exchange is carried out by providing a heat exchanger 36 with a conduit 8 disposed therein in a passage of the waste gases from the combustion furnace 4, and passing air or oxygen through the conduit 8 upstream in the passage of the waste gases.