To enable a metal having reached a temperature of a liquidus or higher to be supplied stably to a plunger by continuously melting chips of a metallic material without using a screw, to reduce the entraining of a slug into a product, and to shorten the time to start-up the operation.

A closed container of a melting tower 2 is composed of a fixed outer cylinder 13 and a rotatable inner cylinder 14, and a preliminary heating chamber 24, semi-melting chamber 25, and a complete melting chamber 26 are formed by the outer cylinder and the inner cylinder. A band heater 15 is equipped on the outside of the outer tower, and a induction coil 16 is equipped on the inside of the inner cylinder. The chips of the metallic material are supplied in the preliminary chamber 24, and the chips of the metallic material in a solid state after preliminary heating is supplied in the semi-melting chamber 25 by the deadweight falling. The chips of the metallic material are heated until becoming a semi-molten state, and the metallic material in the semi-molten state is supplied in the complete melting chamber 26 by falling by the deadweight to melt the metallic material until the complete liquidus or higher. The treatment of the final melting part and the treatment of the first preliminary heating part are carried out simultaneously.