The liquid molten iron is injected in a mold, and gets cooled and coagulated in the course of passing a continuous caster. As a result, such intermediate materials, as slab, bloom, and billet are produced. In the process, bloom turns billet after passing a rolling machine, or is processed as a timber by a rolling machine for timber. Slab is produced as thick plate after passing a rolling machine for plate or is made as hot rolled steel plate after passing a hot rolling machine.