PURPOSE: To improve productivity of a cast billet by arranging a continuously electrode feeding device to a vacuum furnace and also a continuously drawing device for the cast billet and further setting an electrode extension device at outside of the vacuum furnace.

CONSTITUTION: The electrode feeding devices 5a, 5b and the electrode extensions 7a, 7b are arranged to furnace walls 1b, 1c of the vacuum furnace 1 through electrode sealing devices 4a, 4b. The cast billet drawing device 8 is arranged at lower part of the furnace wall 1d at bottom part of the vacuum furnace 1 through cast billet sealing device 4c and power supplying device 6c to the cast billet is set at the most lowest part. At first, dummy bar is used and arc discharge is executed to the same kind of metal piece and the inner part of the furnace is made to vacuum condition. The electric power is conducted to the electrodes 2a, 2b and the dummy bar, to continuously form the cast billet 3. By this method, the cast billet 3 having the optional length is produced and also the change of the electrodes 2a, 2b and taking-out work of the cast billet become unnecessity.