PURPOSE: To decrease the amt. of the residual molten metal by connecting an inductor and the base of a molten metal chamber by a throat having the same sectional shape as the sectional shape of the aperture plane of the inductor and opening the communicating ports of receiving and pouring siphons to the side surface of this throat.

CONSTITUTION: The inductor 2 in the lower part of the furnace body and the base 12 of the molten metal chamber 1 are connected by the throat 3 having the same sectional shape as the sectional shape of the aperture plane of the inductor 2. Further, the communicating ports 5b, 6b of the receiving siphon 5a and the pouring siphon 6a are formed to the side surface of the throat 3. The molten metal surface can be lowered down to a molten metal base surface 12 when the molten metal is supplied under the max. normal pressure via a control device 11 into the molten metal chamber 1 in the furnace body 1a. The remaining of the molten metal in the chamber 1 is thereby obviated. The min. molten metal surface is, therefore, lowered down to the level lower than the base of the chamber 2 and the amt. of the residual molten metal which cannot be poured is drastically decreased.