A diesel engine glow plug having an elongated hollow electrically conductive holder, which holds a rod-like ceramic heater at one end thereof such that one end of the heater extends outside the holder. An external connecting terminal is positioned in the other end of the hollow holder and electrically insulated from the hollow holder. The ceramic heater is a U-shaped heating element with a pair of parallel lead portions made of a resistive ceramic material extending backward from both ends of the U-shaped heating element and arranged such that the outer surfaces of the lead portions are held by the distal end of the holder through electrical insulating layers between the inner surface of the holder and the outer surface of the lead portions. The rear end portions of the lead portions are electrode extraction ends wherein the electrode extraction end of one lead portion is electrically connected to the external connecting terminal through a conductive material and the electrode extraction end of the other lead portion is connected to the metal pipe which itself is electrically connected to the holder through a conductive material.