PROBLEM TO BE SOLVED: To solve such a problem of a conventional nonthermal equilibrium plasma ignition plug or nonthermal equilibrium plasma ignition device that the amount of plasma generation is not sufficient, and whereby the ignition performance cannot be enhanced sufficiently.SOLUTION: A nonthermal equilibrium plasma ignition plug includes a cylindrical main body metal fitting having a shaft hole extending in the axial direction, an insulator disposed to form a gap between the inner surface of the shaft hole at the tip of the main body metal fitting, and held by the main body metal fitting, and a center electrode held in the center of the insulator, and generates nonequilibrium plasma depending on the voltage applied from the power supply to the ignition plug. On the surface of the insulator facing the surrounding discharge space, a plurality of recesses or protrusions are formed.SELECTED DRAWING: Figure 1
