PROBLEM TO BE SOLVED: To make a structure in which a tubular dielectric 3 is hard to break. SOLUTION: A plasma generating part 12 included in a plasma device 100 is formed on a tubular dielectric 3 having an inner space which is a flow path of a plasma generating gas supplied from a supply source and an inner space of the tubular dielectric 3. An internal electrode 4 that is arranged and extends in the axial direction of the tubular dielectric 3, an external electrode 5 that is arranged at a position facing the internal electrode 4 along the outer peripheral surface of the tubular dielectric 3, the tubular dielectric 3, and the external electrode. It has a body portion that covers the surface of 5, and the body portion 2b has a first divided body 2d and a second divided body 2e that are divided into two by a cross section extending in the axial direction of the irradiation device, and is a first divided body. The 2d and the second divided body 2e have an inner peripheral surface 2f having a shape that is in surface contact with the outer peripheral surface of the tubular dielectric 3, and a part of the inner peripheral surface is in surface contact with the surface of the external electrode 5. The first concave portion 2h of the shape is provided. [Selection diagram] Fig. 6【課題】管状誘電体３が壊れにくい構造にする。【解決手段】プラズマ装置１００が有するプラズマ発生部１２は、供給源から供給されたプラズマ発生用ガスの流路である内空部を有する管状誘電体３と、管状誘電体３の内空部に配置され、管状誘電体３の軸線方向に延びる内部電極４と、管状誘電体３の外周面に沿って内部電極４に対向する位置に配置される外部電極５と、管状誘電体３及び外部電極５の表面を覆う胴体部と、を有し、胴体部２ｂは、照射器具の軸線方向に延びる断面で２分割された第１分割体２ｄ及び第２分割体２ｅを有し、第１分割体２ｄ及び第２分割体２ｅは、管状誘電体３の外周面に面接触される形状の内周面２ｆを有し、内周面の一部には、外部電極５の表面に面接触される形状の第１凹部２ｈが設けられる。【選択図】図６
