PURPOSE:To manufacture a high-Mn ferrous alloy inexpensively in high efficiency by charging with Mn ore, solid carbonaceous material and slagging agent a reaction vessel charged with molten metal and molten slag and by carrying out heating, melting and reduction under specific conditions. CONSTITUTION:The molten high-Mn ferrous alloy and the slag are left in the top and bottom blown convertor-type reaction vessel by about 10-50% of the rated capacity of the vessel, into which oxygen and the like are blown via a bottom blowing nozzle. Subsequently, the vessel is charged with the carbonaceous material, into which oxygen is blown via a top blowing lance, and the furnace is then continuously charged with the Mn ore and/or its preliminary reduced substance, carbonaceous material and slagging agent. At this time, heating and melting are carried out with maintaining the temp. of the molten metal at 1,500 deg.C+alpha (where alpha