PURPOSE: To burn a solid substance without the generation of smoke by a method wherein dry distillation reactions are allowed to take place in a sealed vessel and gasses generated in the vessel are taken out to be burned.

CONSTITUTION: The disused material 40 moves down as it is burned and decomposed in a primary combustion zone 38 and the entry of air into the zone from above is prevented so that the primary combustion is limited. A primary gas current generating due to the primary combustion is introduced into a communication hole 42 after passing along the upper part of a combustion chamber 31 while a secondary air current is introduced into the communication hole 42 after passing along the lower part of the chamber 31. As a result, the primary gas current and the secondary air current are heated and the so called diffusion combustion is made in the combustion chamber 31. Next, the mixed gas current G introduced into the communication hole 42 makes itself a swirling current and the high temperature gas moves upward in the form of a current as shown by the arrow and is discharged from an exhaust cylinder 43. Further, low temperature gas, ashes and dust move down along the side wall of the vessel and are introduced into a dust collecting chamber 35 through a communication hole 44 due to a centrifugal force so that they are purified through a filter 45, transferred to an ejector 48 and discharged outside the system through the exhaust cylinder 43 to thereby burn the disused material without the generation of smoke.