To provide a closed sealing device for an electroslag melting furnace for completely preventing atmosphere from flowing into a mold even when a hood is installed thereon.

In the closed sealing device for an electroslag melting furnace, a heat resistant gas outflow hood is provided on an upper part of a copper mold 1. An opening between an inner peripheral surface of the upper end flange 4 of the hood, and an outer peripheral surface of a jig 6 connected to an upper part of a consumable electrode 5 inserted in the mold is sealed, so as to prevent atmosphere from flowing into the mold. A fixing plate 11 is installed on a power supply part 8 connected to the upper part of the jig. A heat resistant cylindrical cover body 12 is connected to the fixing plate perpendicularly thereto so as to cover a gap between the jig and the upper flange 2 of the mold to close and seal the gap, and so as to freely adjust its length in a cylindrical direction. Gas filled in a space sealed by the fixed fitting or the cover body is discharged through an opening 15.