A cylinder head for use in an internal combustion engine, the engine having a combustion chamber formed by a cylinder block that is penetrated by a cylinder, and having a piston which fits into the cylinder so as to reciprocate freely, the cylinder head being for assembly on the cylinder block and integrated with plasma apparatus (810, 820, 830, 840), the plasma apparatus comprising: a discharge device with an electrode (812, 813) exposed to the combustion chamber and installed in the cylinder head; an antenna installed to protrude from the cylinder head into the combustion chamber; and an electromagnetic wave transmission line installed in the cylinder head and with one end connected to the antenna and the other end, covered with insulator or dielectric, penetrating the cylinder head to extend to an outer wall of the cylinder head, the electromagnetic wave transmission line being configured to receive electromagnetic waves fed from an electromagnetic wave generator, wherein the plasma apparatus is configured to generate discharge with the electrode (812, 813) of the discharge device and to radiate from the antenna the electromagnetic waves fed from the electromagnetic wave generator through the electromagnetic wave transmission line, characterized in that: a bulging portion bulging from the cylinder head to the combustion chamber covers the antenna and is made from insulator or dielectric; and the antenna edge aims at the electrode (812, 813) of the discharge device; and/or the discharge device is installed in the cylinder head such that the electrode (812, 813) is placed in the vicinity of the center of the combustion chamber when the cylinder head is assembled on the cylinder block, and a plurality of antennas queue up from the electrode (812, 813) toward a portion corresponding to a cylinder wall on the cylinder head, when viewed from the direction of reciprocation of the piston. a discharge device with an electrode (812, 813) exposed to the combustion chamber and installed in the cylinder head; an antenna installed to protrude from the cylinder head into the combustion chamber; and an electromagnetic wave transmission line installed in the cylinder head and with one end connected to the antenna and the other end, covered with insulator or dielectric, penetrating the cylinder head to extend to an outer wall of the cylinder head, the electromagnetic wave transmission line being configured to receive electromagnetic waves fed from an electromagnetic wave generator, wherein the plasma apparatus is configured to generate discharge with the electrode (812, 813) of the discharge device and to radiate from the antenna the electromagnetic waves fed from the electromagnetic wave generator through the electromagnetic wave transmission line, a bulging portion bulging from the cylinder head to the combustion chamber covers the antenna and is made from insulator or dielectric; and the antenna edge aims at the electrode (812, 813) of the discharge device; and/or the discharge device is installed in the cylinder head such that the electrode (812, 813) is placed in the vicinity of the center of the combustion chamber when the cylinder head is assembled on the cylinder block, and a plurality of antennas queue up from the electrode (812, 813) toward a portion corresponding to a cylinder wall on the cylinder head, when viewed from the direction of reciprocation of the piston.