An ignition coil is provided with a primary coil, a secondary coil, a center core, and an outer core. The primary coil, secondary coil, the center core, and the outer core are accommodated inside a case, the inside of the case is filled with a resin filler having electrical insulating properties. The case has an opening member which opens to an upper-side of a vertical direction, a side wall section formed by the opening member, and a bottom member covering a lower-side of the side wall section. A circular cover member, formed on the opening member, provided with a through opening which passes through the inner-side of the opening member in the vertical direction.