GAS ANALYZER

An elongated ferromagnetic anodic electrode is fixed to a tightly closable pipe shape vacuum casing so as to extend within the casing as a cantilever and magnetic field applying module is disposed so as to concentrate magnetic field at a tip side position of the ferromagnetic anodic electrode in an area of discharge optical emission when a high voltage is applied between the anodic electrode and the vacuum casing as a cathode electrode. In addition, a vacuum casing can be formed with a ferromagnetic and soft magnetic material for magnetic flux to be permeable well, or a tip side alone of an anodic electrode rather than the anodic electrode itself can be formed with a ferromagnetic material, or a ferromagnetic member can be disposed at a near position of an anodic electrode, so as to concentrate magnetic field in a vicinity of a tip of an anodic electrode.