To surely control MgO ratio in non-metallic inclusion to ≤2.5% by controlling MgO quantity.

When steel for high strength steel wire is manufactured, in a process from the molten steel tapping-off time in a converter to a secondary refining treatment, the MgO quantity to be added into the molten steel is controlled to be ≤330g/t of the molten steel, and in the decarburize-treatment in the converter, [P] in the molten iron to be charged into the converter is controlled to be ≤0.040 mass%, and the CaO quantity to be supplied is controlled to be 12.0-21.0 kg/t in specific consumption. The MgO quantity to be supplied is controlled to be 100-1500g/t of the molten steel. Regarding a top-blowing, the blowing oxygen quantity in a primary top-blowing section in 60-80% of time from the blowing start is made different from the blowing oxygen quantity after the elapse of the above time. Regarding a bottom-blowing, the bottom-blowing gas is blown from blowing start to blowing finish so as to satisfy 0.045-0.075Nm3/min/ton of the molten steel and 0.040-0.064Nm3/min/mm2. In addition to the above conditions, a flux used at the time of ladle-refining is made to have a prescribed composition.

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