To dispense with degassing process in a melting furnace, to smoothen the working process, to make it possible to charge an ingot into the furnace by rolling down so as to reduce the labor of a worker and to prevent the danger of burn by executing the degassing at the time of forming the ingot and forming into the spherical shape.

The molten metal quantity in a holding furnace 12 is compared with a prescribed reference quantity in a control device 13 with a signal transferred from an incorporated quantity measuring instrument 11 of the molten metal, and at the time of becoming the reference quantity or lower, the signal is transferred to a shut-off device 7 and a counting device 10. A trough-stage passage for charging body 5 is opened by rising a damper 8 and the number of the rolled-down spherical ingots 1 is counted with the counting device 10 and this signal is transferred to the control device 13. In the case the counted number reaches a prescribed reference value, the trough-state passage for charging body 5 is shut off with the shut-off device 7. By this constitution, the shortage of the molten metal can be supplemented by automatically charging the needed number of the spherical ingot 1 according to the molten metal quantity in the holding furnace 12.