An ignition coil includes a primary coil, a secondary coil, a center core, a side core, a core cover, a case, and an insulating resin. The core cover is formed in a form that covers an inner side face, one thickness direction end face, and an other thickness direction end face of the side core. Wall portions that divide a mass of the insulating resin into portions, or reduce an amount thereof, are provided in the core cover on an aperture portion side of the case, which is the one thickness direction end face side of the side core.