A gasket for use in an internal combustion engine when installed between a cylinder block and a cylinder head of the engine so that its opening corresponds to a cylinder of the engine, wherein in the engine a piston fits into the cylinder and reciprocates freely, the cylinder penetrates the cylinder block, and the cylinder head is assembled on the anti-crankcase side of the cylinder block to create a combustion chamber with the piston and the cylinder, the gasket comprising: at least one discharge line installed in an intermediate layer in a thickness direction, having an outer end exposed from the outer peripheral edge to be a first connection part and an inner end exposed from a inner peripheral edge around the opening to be an electrode, and configured such that discharge is generated between the electrode and an earth member around it with voltage applied between the first connection part and the earth member, or such that, when there is a plurality of discharge lines, discharge is generated between the electrodes (762, 762) with voltage applied between the first connection parts (761, 761), characterised by: an antenna installed at least partly in the intermediate layer in the thickness direction at the inner peripheral edge around the opening and configured to radiate electromagnetic waves into the combustion chamber; and an electromagnetic wave transmission line installed in the intermediate layer in the thickness direction, having an outer end exposed from the outer peripheral edge to be a second connection part and an inner end connected to the antenna, for guiding electromagnetic waves to the antenna, wherein the or each discharge line, the antenna, and the electromagnetic wave transmission line are electrically insulated from both surfaces of the gasket in the thickness direction. at least one discharge line installed in an intermediate layer in a thickness direction, having an outer end exposed from the outer peripheral edge to be a first connection part and an inner end exposed from a inner peripheral edge around the opening to be an electrode, and configured such that discharge is generated between the electrode and an earth member around it with voltage applied between the first connection part and the earth member, or such that, when there is a plurality of discharge lines, discharge is generated between the electrodes (762, 762) with voltage applied between the first connection parts (761, 761), characterised by: an antenna installed at least partly in the intermediate layer in the thickness direction at the inner peripheral edge around the opening and configured to radiate electromagnetic waves into the combustion chamber; and an electromagnetic wave transmission line installed in the intermediate layer in the thickness direction, having an outer end exposed from the outer peripheral edge to be a second connection part and an inner end connected to the antenna, for guiding electromagnetic waves to the antenna, wherein the or each discharge line, the antenna, and the electromagnetic wave transmission line are electrically insulated from both surfaces of the gasket in the thickness direction. an antenna installed at least partly in the intermediate layer in the thickness direction at the inner peripheral edge around the opening and configured to radiate electromagnetic waves into the combustion chamber; and an electromagnetic wave transmission line installed in the intermediate layer in the thickness direction, having an outer end exposed from the outer peripheral edge to be a second connection part and an inner end connected to the antenna, for guiding electromagnetic waves to the antenna, wherein the or each discharge line, the antenna, and the electromagnetic wave transmission line are electrically insulated from both surfaces of the gasket in the thickness direction.