PURPOSE: To produce molten steel by an operation method in which not only utilizing efficiency of the heat for melting is improved, but also the environmental conservation field is considered, in the method of producing the molten steel from a solid iron source.

CONSTITUTION: The iron source and a solid carbon source respectively preheated are charged into a vessel for melting and melted with arc heat to form the molten iron having 0.3-2.0 wt.% carbon content. Successively, the iron source and the solid carbon source respectively preheated in the same way, are charged into the molten iron and when melting with heat generated by the reaction between oxygen and carbon, oxygen is introduced into the molten iron in the vessel for melting through a nozzle set below the molten iron surface and the molten iron is refined until ≤0.4 wt.% carbon content. During introducing the oxygen into the molten iron, a gas containing oxygen is introduced to the upper part of the molten iron surface in the vessel for melting. A exhaust gas produced in the molten iron in these processes is used for preheating the iron source. After refining, the molten steel is taken out of the melting use vessel.