PURPOSE: To suppress the occurrence of a surge even when a high voltage is applied across a conductor by putting a surge suppressing device constituted by coating cores formed by alternately winding a magnetic material and insulating sheet many turns in an overlapping state with insulators on the conductor housed in a grounded container.

CONSTITUTION: The surge energy of a high-frequency surge intruded into a conductor 3 housed in a metallic container is absorbed by a magnetic material 8, such as an amorphous metal, etc., having a large hysteresis loss. Each layer of the magnetic material 8 is sufficiently insulated from another by an insulating sheet 9 alternately wound with the material 8 in an overlapping state and each core 10 is insulated from another by an insulator 11. Consequently, the material 8 does not cause any insulation breakdown between layers and between cores 10. Therefore, the generation of a surge having high energy in a gas-insulated device and the intrusion of a surge having high energy into the gas-insulated device can be suppressed.