A discharge device of the present invention including a pair of electrodes opposingly disposed in a sealed tube is characterized by the provision of a conductive member surrounding one of the electrodes in the sealed tube. An ignition system with a series gap has a built-in discharge device provided with a series gap, with one end connected to the center electrode side of the spark plug and with the other end connected to the high-tension cable side extending from the high-voltage distribution side. In this ignition system, a discharge device has a conductive member which surrounds one of the electrodes of the sealed tube, and one of the electrodes enclosed with the conductive member of this discharge device works as a cathode. Furthermore, in this ignition system with a series gap which includes a discharge tube provided with the series gap with one end connected to the center electrode side of the spark plug and the other end connected to the high-tension cable extending from the high-voltage distribution side, there is provided a conductive member enclosing the cathode side of the discharge device to be installed in the casing.