PURPOSE: To decrease the disconnection of a core rod wire by a bell and to decrease the cracks to be generated in the core rod wire by the bells by heating the part near a nozzle to maintain the molten metal temp. in the bottom of a crucible to a melting temp. or above, by which the bell is no longer generated.

CONSTITUTION: A controller 12 drives a 1st induction heating coil 9 of a crucible 1 at a high frequency and heats the part near the nozzle 5 in accordance with the present temp. of molten copper 2 in the bottom of the crucible detected by a temp. sensor 11 during operation. The temp. of the molten copper 2 in the bottom of the crucible is maintained at the melting temp. or above. Even if, therefore, the tip of the nozzle 5 causes frost setting, the molten copper 2 at this tip part is prevented from falling to the m.p. or below and solidifying. Consequently, the bell is no longer generated. Further, the flow of the molten copper 2 from an outer annular storage layer 15 to an inner annular storage layer 16 arises and the stagnation of the molten copper 2 is not formed near the inner aperture of the nozzle 5; therefore, the generation of the bell is surely prevented.