An ignition coil includes a coil body, a plug connection portion protruding from the coil body, and a connector for electrically connecting the ignition coil to an outside. In the coil body, a primary coil is arranged on an inner peripheral side of a secondary coil, and a center core is arranged on an inner peripheral side of the primary coil. The secondary coil includes a secondary electric wire having thereon an insulating film, wound around an outer periphery of a resinous secondary spool. Furthermore, the connector is formed integrally with an end of the secondary spool in an axial direction.