To provide a combustion furnace for a mixture of waste and its combusting method having a structure for reversing the combustion furnace, so that the combustion is evenly performed, and a combustion gas is treated in a high temperature zone.

In this combustion furnace for the mixture of waste, a cylindrical combustion furnace body 1 is mounted in a state of being forwardly and backwardly rotatable, the combustion furnace is provided with a filament cap 2 at its one end, and a pressure feeding device 3 for a combusted substance S at the other end, and further a plurality of scraping-off plates 4 are spirally mounted in the axial direction of a furnace inner wall to longitudinally move the combusted substance X. In this combusting method, the wood and cake in the combusted substance X are combusted first to produce combusted charcoal, then the other combusted substance is pressure-fed into the combustion furnace to be combusted, the unevenness in combustion is solved by rotating the combustion furnace with respect to the uncombusted substance, and the combusted substance is retained in the furnace until the waste is completely burnt out to be combusted.