To provide a structure in which efficiency of contact of treated material with plasma active species is improved, and treatment efficiency of the treated material is improved by this in a device in which the plasma is generated from a gas and plasma treatment of the treated material is carried out.

In an electrode device 30 for generating the plasma, the electrode device 30 is provided with a substrate 40 consisting of dielectrics, a first electrode 8 embedded in the substrate 40, and a second electrode 6A installed at one principal plane 7a of the substrate. A through hole 26 to supply plasma gas to the substrate 40 is formed in the substrate 40, and the plasma is generated by creeping discharge to occur along the substrate 40 from the second electrode 6A.