NOVELTY - The device (C) has a conductive body (20) arranged between a pair of devices in an electric circuit. An explosive type gas generator (40) is arranged away from the conductive body. A cutting unit (50) is moved by gas from the gas generator to cut the conductive body, and divides the conductive body into a first cut piece and a second cut piece and breaks the conduction between the devices. The body is cut by the cutting unit in an arc-extinguishing chamber (32), where an arc occurs between a cut end of the first cut piece and a cut end of the second cut piece extinguished in the chamber.    USE - Device for breaking conduction between a storage battery i.e. fuel cell, and an electric device i.e. vehicle driving motor, in a fuel cell vehicle.    ADVANTAGE - The device configures communication passage of the cutting unit of the hole formed on the main body and a hole through an interior of the blade such that opening at the tip of the communication passage can be formed to be tapered toward the tip surface, so that a flow passage area decreases toward the tip of the tapered opening, and the flow rate of gas increases toward the tip, thus strongly blowing gas between the cut ends from the opening, and hence efficiently blowing off the arc. The device moves blade in an area close to a cutting edge portion along a longitudinal direction of a breakable portion, where the breakable portion is cut between the blade and the cutting edge portion, so that the extension due to the cutting of the conductive body is made less, and the interval between the cut ends is shorter, thus easily extinguishing the arc in the arc-extinguishing chamber when the arc occurs between the cut ends due to cutting of the breakable portion, and hence reducing an impact of the arc on the conduction breaking device as compared with the device without a measure against an arc.    DETAILED DESCRIPTION - The conductive body is a rectangular plate shaped conductive body.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a conduction breaking device.    Conduction breaking device (C)    Conductive body (20)    Arc-extinguishing chamber (32)    Explosive type gas generator (40)    Cutting unit (50)    Cylindrical main body (51)    Blade (52)