A dual line ceramic glow plug uses a ceramic heater as an incandescent body which protrudes from the bottom of a metal fitting and which is made of an incandescent wire of a refractory metal embedded in a sintered ceramic powder. The bare ends of the incandescent wire terminate in a pair of metal terminal fittings secured to the end of the ceramic heater within the metal fitting. Electrical leads protruding from the terminal fittings are welded to a pair of terminal electrodes projecting outwardly from the top of the metal fitting. The ceramic heater is held in position by a metal sheath that is slipped over and bonded to the middle portion of said heater. The middle portion of the ceramic heater is brazed to the inner surface of the metal sheath in electrically insulated relation thereto with an intervening glass layer formed on the outer surface of the ceramic heater.