An internal combustion engine ignition coil device has an annular seal rubber at its lower side coil. An annular projection is provided on a part of the seal rubber and is pressed against the inner diameter surface of a plug hole. An air path is formed in part of a coil case by mounting the seal rubber into a groove, enabling inside and outside portions of the plug hole to communicate. A gas-permeable thin film resin member is bonded to an inlet of the air path.