An ignition coil includes a cylindrical portion that includes a primary coil and a secondary coil, which are coaxially wound. The cylindrical portion can be inserted into a plughole of an engine. The cylindrical portion has a tip end in an axial direction thereof. The tip end of the cylindrical portion has a plug mounting hole, into which a sparkplug is mounted. The plug mounting hole accommodates a high voltage terminal, which electrically connects with one of the secondary coil, and a coil spring, which makes contact with the high voltage terminal. The cylindrical portion has a base end portion in one axial end thereof. The base end portion of the cylindrical portion includes at least one flange portion. The at least one flange portion radially outwardly protrudes. The at least one flange portion has multiple bolt insertion holes, through which a bolt is respectively inserted.