PURPOSE: To efficiently remove gas and inclusion, by blowing inert gas of a prescribed quantity and a Ca compound steel refining agent into molten steel, from a discharge hole of the lower part of an agitating shaft which is rotated at a prescribed rotating speed.

CONSTITUTION: A rotary agitating device having an inert gas lead-in pipe on the inside of a rotary shaft 2, and having an agitating blade 4 and a discharge hole 5 on the lower part of the shaft 2 is installed to a molten metal vessel 1. Subsequently, rotational frequency of this agitating device is set to ≥50rpm, a ratio of inert gas is set to 1W500Nl/min. Ton steel, and also a pulverulent body consisting of 1 kind or more among CaO, CaCO3, CaF2, etc. is blown into molten steel together with said gas. In this way, the inert gas is fined, and gas and inclusion are removed efficiently.