PURPOSE: To stabilize and automatize molten metal surface level by finding changing ratio of molten metal surface level till the molten metal reaches to a first level and correcting molten metal pouring quantity based on comparison with the setting changing ratio of the level.

CONSTITUTION: The molten metal surface level gage 7 is arranged in a mold 4 and a PID controller 15 connecting with a molten metal surface decision device is arranged. After starting pouring of the molten metal, when the molten metal surface level exceeds the first level, the lapse of time is measured through the level gape 7, a time decision device 17 and an opening degree computing element 14, to operate the changing ratio of the molten metal surface level. Successively, in order to correct the molten metal pouring quantity by comparison with the setting level changing ratio, the opening degree of a stopper 6 is corrected through a control panel 11. After securing the changing ratio of the molten metal surface level according to the rule, as it is changed to the feedback control, the control of the molten metal surface is stabilized and perfectly automatized.