PURPOSE: To treat suspended oxides, and to improve the precision in refining molten steel by adding a liquid or a solid phase having smaller sp.gr. than molten steel and a size larger than the mean distance between particles of suspended oxide remaining in the molten steel to the melt.

CONSTITUTION: A liquid and/or solid phase having smaller sp.gr. than molten steel and a size larger than the mean distance between particles of suspended oxide remaining in the molten steel is added into the melt as a turbulent flow at the initial stage of a metallurigical treatment, and the suspended oxides remaining and convecting in the molten steel especially in the molten aluminum killed steel is treated to improve the precision of refining and the surface quality of the cast material and to reduce the amt. of oxide inclusions. A metallurgical slag capable of regulating the surface tension and the liquid drop by changing the composition can be preferably used as said liquid phase, and a solid material such as MgO, CaO, and SiO2 consisting of particles having an appropriate size and whose m.p. is higher than the treating temp. of the molten steel is used as the solid phase.