A plug connector capable of increasing the sealing between a rubber member and an outer circumferential surface of a spark plug insulator for improvement in current leakage resistance. The plug connector includes a conductive part that electrically connects a spark plug and a power supply member for power supply to the spark plug; and a rubber member that covers the conductive part. The spark plug has an insulator and a terminal electrode protruding toward the rear from a rear end of the insulator. The plug connector further includes a ring member arranged on an outer circumference of the rubber member.