A gasket of an internal combustion engine includes a discharge line installed in an intermediate layer and having an outer end exposed from the outer peripheral edge of the gasket to be a first connection part and an inner end exposed from a inner peripheral edge around the opening to be an electrode, configured such that discharge is generated between electrodes with voltage applied between first connection parts; an antenna installed at least partly in the intermediate layer at the inner peripheral edge around the opening to radiate electromagnetic waves into a combustion chamber; and an electromagnetic wave transmission line installed in the intermediate layer, having an outer end exposed from an outer peripheral edge to be a second connection part and an inner end connected to the antenna, and guiding electromagnetic waves to the antenna.