To improve the quality of slag produced by means of a pyrolytically gasifying melting system.

Solid matters are separated from a pyrolysis gas generated in a fluidized bed gasifying furnace 1 by means of a solid-gas separating device 2 interposed between the furnace 1 and a revolving melting furnace 3 and the separated solid matters are thermally cracked and gasified by repeatedly returning the matters to the furnace 1. On the other hand, the separated pyrolysis gas is introduced to the melting furnace 3. Since the matters accompanying the pyrolysis gas are only an object to be melted, such as dust composed mainly of fine fly ash, etc., the object to be melted can be melted surely without variation.