Abstract: An industrial waste and household waste is treated by a pyrolysis step for carbonizing waste containing organic substance in a condition sealed from an air so as to separate to a pyrolysis gas and a pyrolysis residue; a gas cracking step for introducing the pyrolysis gas after the pyrolysis step so as to react an oxide component in the pyrolysis gas through an oxidization reaction and thermally decompose high molecular hydrocarbon in the pyrolysis gas with a heat generated by the oxidization reaction so as to obtain a cracked gas containing low molecular hydrocarbon; a residue cooling step for cooling the pyrolysis residue generated in the pyrolysis step for solidification; a mechanical processing step for crushing and sorting the pyrolysis residue solidified in the residue cooling step so as to obtain a pyrolysis char essentially consisting of pyrolysed organic substance and inorganic components; and a smelting and gasifying step for burning the pyrolysis char obtained in the mechanical processing step at a