PURPOSE: To contrive to lower the degree of oxidation of a slag and to enhance the yields of Fe and Mn by a method wherein oxygen gas and an inert gas are blown downwardly through different nozzles, when refining a steel while whirling or oscillating a multinozzle lance.

CONSTITUTION: In the top-blown converter steelmaking method wherein refining is conducted while whirling or oscillating a multinozzle lance, oxygen gas is fed through all the nozzles during the initial and intermediate stages of the refining, and when the final stage is reached, a part of the nozzles is switched over so as to feed on inert gas therethrough. In this way, the effective collision energy with which the top- blown gas impinges against the molten pig iron is increased, whereby the slag and the molten steel are stirred effectively, and the CO partial pressure in the atmosphere inside the furnace is lowered. By this method, the degree of oxidation of the slag can be lowered and the yields of Fe and Mn can be enhanced, even in the case of melting a low carbon steel.