PURPOSE: To provide a quick raised temp.-saturated temp. type ceramic glow plug by installing a rod-like ceramic heater of which heating wire is made of high melting point metal having more than a definite value of resistance change rate to temp., is buried in a ceramic sintered body having more than a definite value of heat conductivity, and which is exposed from the end of an outer metal cylinder with a certain length and cross section area of which is restricted.

CONSTITUTION: A pure tungsten wire having a resistance change rate to temp. such as RT/R25=about 2.7 at RT=800°C is buried in silicon nitride powder which may become sintered body of silicon nitride having a heat conductivity of 0.03cal/cm sec.°C, and a rod-like silicon nitride heater is obtained after being sintered by hot press process. The exposed length L of the rod-like ceramic heater from the tip of an outer metal cylinder is taken as 2≤L≤7.5mm and cross section area thereof is taken as 3≤S≤13mm2. When cross section area S of the rod-like ceramic heater is fixed at S=13mm2 and the length L of the exposed part from the tip of the out-metal cylinder 6 is set to L=14mm, 7.5mm, and 6mm, the resistance change rate to temp. as shown in the graph is reduced in proportion to reduced length of the exposed part.