<p>In a plasma torch A, a valve 10 is provided to a gas supply path 8 for supplying a plasma gas inside or in a vicinity of the plasma torch A, a closing operation of the valve 10 is approximately synchronized with a change in the electric current at the time of stopping a plasma arc. The valve 10 is provided on a position separated from the front end 4b of the plasma torch by within a range of a distance of 600 mm.
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