Abstract: The invention relates to a refining lance used in blowing some additive into molten metal in a vacuum vessel when molten metal, such as molten steel, refined by employing a converter or electric furnace or the like is further refined into a metal having the desired composition. The lance includes a center hole for jetting the additive in the presence of gas and a plurality of side holes (Laval nozzle holes) for supply of accelerating gas so as to have the additive effectively added to the molten metal. The invention also proposes a method for producing low-carbon high-purity steels in molten state by using the refining lance.