Provided is a plasma apparatus using a cylinder head, which comprises a discharge device installed with an electrode exposed to the combustion chamber and installed in the cylinder head, an antenna installed to protrude from the cylinder head into the combustion chamber, a bulging portion bulging from the cylinder head to the combustion chamber so as to cover the antenna, made from insulator or dielectric, 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, and an electromagnetic wave generator for feeding electromagnetic waves to the electromagnetic wave transmission line. At compression stroke, discharge is generated with the electrode of the discharge device and the electromagnetic waves, fed from the electromagnetic wave generator through the electromagnetic wave transmission line, are radiated from the antenna.