To surely extinguish a produced arc, by surely fixing an arc spot on the outer end side of a movable electrode.

A movable electrode 9 is formed substantially into an L-shape and inclined by providing an arc-resistant metal 11 so that the outer end 9b side is finally separated from a fixed electrode 6. A slit part 12b in an arc- extinguishing chamber 12 is formed by connecting a slit part 12c for movable electrode passage with a narrowest slit part 12d that is a slit narrower than the thickness of the movable electrode 9 and formed on the outer end 9b side of the movable electrode 9 finally separated from the fixed electrode 6. A magnetic body 13 is attached on an outer surface of a slit wall 12j on the side of the narrowest slit part 12d.