To provide an inexpensive apparatus by efficiently carrying out a complete combustion and a neutralizing process for suppressing the synthesis of dioxin using the characteristics of a swirl flow.

A furnace main body is divided into a first-stage swirl fluid bed chamber, a second-stage gas swirl flow chamber and a gas combustion chamber from a bottom surface. A gas cooling chamber with a helmet is provided on the top part of the central axis of the second-stage gas swirl flow chamber. A cooling water outlet and a cooling water inlet provided on the side plate of the gas cooling chamber communicate with the top part of the central axis of the helmet to lower the temperature of combustion exhaust gas to prescribed temperature. In the lowermost part of the gas cooling chamber, many orifice nozzles are provided in an annular air diffusing pipe to agitate combustion flying ash in waste water generated by cooling water. An exhaust gas chamber and a white smoke preventing hot air inlet are provided on the top part of the central axis of the gas cooling chamber. Many orifice nozzles are provided in the lower part of an exhaust tube and an annular wind box is provided outside the side plate. High pressure air in which a heat exchange is carried out outside the furnace is supplied to the annular wind box to form a third-stage swirl flow, vaporize steam in the exhaust gas and prevent white smoke.