Abstract: An ignition device for internal combustion engine including a spark plug containing a housing, an insulator having a central electrode and a sidewall electrode attached to the housing and forming a spark gap between the sidewall electrode and the end of the center electrode, where the space around the spark gap is covered with the internal conic surface of the housing expanding outwards, and a capacitive electric energy storage device attached to the spark plug, whereas the housing of the spark plug includes an attachment and a base part, whereas the attachment includes an internal conic surface expanding outwards and a slot for sidewall electrode.