To use effectively a high temperature exhaust gas by inhibiting regeneration of polychlorinated-disbenzo-p-dioxins by a method wherein a fly ash exhausted from a waste incinerator is removed from in the high temperature exhaust gas by collecting dusts within a specific temperature range with a ceramic filter.

Though traces of a heavy metal group containing mercury or the like are contained in an exhaust gas exhausted from a waste incinerator, in order to decompose the polychlorinated-dibenzo-p-dioxins, their complete combustion at 800°C or higher in the incinerator is necessary and indispensable. However, a controversial point wherein though the polychlorinateddibenzo-p-dioxins are decomposed by the incineration treatment, the polychlorinated-dibenzo-p-dioxins come to be regenerated by a gas and solid reaction in which a gas phase reaction on and after an outlet of the incinerator and a surface of a fly ash participate, is generated. In order to solve this problem, the fly ash is treated so a to be removed by collecting dusts at 450 to 800°C with a ceramic filter from the exhaust gas at a high temperature exhausted from the waste incinerator. In this case, the ceramic filter to be used is made of honeycomb ceramics of 3 to 15 μm in an average pore diameter.