PURPOSE: To enable surface analyze of a specimen with a rough surface by providing a tube for flowing an inert gas such as Ar in a groove located outside an O ring for dual shield and by introducing the inert gas therein.

CONSTITUTION: A gas introduction tube 16 for introducing inert gas such as argon is provided outside an O ring 14 for maintaining a vacuum degree, and an O ring groove 15 n in which an O ring 17 is titled is provided. The inert gas is introduced through the gas introduction tubes 8, 16 and is exhausted through the gas exhaust tubes 10, 11, and when a high voltage is applied between an electrode 2 and an electrode 7, the inert gas is ionized to produce positive ions, and since a specimen 1 is suppered the excitation and the emission are generated, after atoms in the specimen 1 are scattered. At this time, since the inert gas is pressed into a glow discharge device through the rough surface of the specimen from the gas introduction tube 16, the impure gases such as oxygen and nitrogen in the atmosphere cannot be enter. As a result, even when a specimen with a rough surface allowed to is analyzed, it is possible to carry out the stable glow discharge.