An ignition device for a plasma jet ignition plug is provided. A resistance for decreasing electric noises is not incorporated in a plasma jet ignition plug. A resistance of not less than 1KΩ and not more than 20KΩ is provided to a path from a spark discharge circuit to a center electrode, thus reducing the generation of electric noises at the time of trigger discharge. Along with the reduction of the generation of electric noises, a loss of energy at the time of plasma discharge can be reduced by setting an inner resistance provided to a line extending to the center electrode from a plasma discharge circuit to 1Ω or less. Accordingly, the plasma jet ignition plug can jet flame-shaped plasma sufficiently large for igniting an air-fuel mixture.