IGNITOR OF INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To perform creeping discharge along a top surface of a piston by fixedly providing an ignition electrode on a cylinder head in a condition of being insulated from the cylinder head by a first dielectric, and covering at least a part of the top surface of the piston with a second dielectric. SOLUTION: A second dielectric 9 has a dielectric constant larger than a dielectric constant of an electrode holding body 6 being a first dielectric. When a piston 3 slidingly moves toward the upper dead center when an internal combustion engine is operated, high voltage is impressed on an ignition electrode 5 from a high voltage source 8, and spark discharge is generated in a discharge passage as shown by a continuous line (a) from the ignition electrode 5. That is, the spark discharge flows in the radial direction of the piston 3 along a top surface of the piston 3 on the piston side dielectric 9 through discharge in gas flowing in a combustion chamber 4 toward a part opposed to the ignition electrode 5 of the top surface of the piston 3 from the ignition electrode 5, and is absorbed by a cylinder 1 in an outer peripheral position of the top surface of the piston 3 or in its vicinity place.