To provide a heat recovery method, a combustible treating method, a heat recovery apparatus and a combustible treating apparatus dispensing with a facility such as a water spray type gas cooling facility while minimizing the margin ratio of a heat transfer face by melting ashes without needing assisting fuel even in the case of combustible waste of low calorific power, and restraining the ashes from sticking to the heat transfer face of the heat recovery apparatus even when recovering heat from combustion gas after melting the ashes.

The combustible treating apparatus is provided with a fluidized bed gasifying furnace 1 for gasifying supplied combustibles to produce first gas G2 and second gas G1 containing particles; the heat recovery apparatus (a boiler 3) for leading in the first gas G2 to exchange heat with a heat receiving fluid and to recover heat; and a melting furnace 2 for leading in the second gas G1 to melt the ashes. A gas lead-in means is further provided for leading in gas G3 exhausted from the melting furnace 2, as transport gas of particles further generated in the melting furnace 2, together with the particles into the heat recovery apparatus (the boiler 3).