Glow plug fitted with combustion pressure detection sensor

A glow plug in which a convex portion (70) is formed in an outer peripheral surface (10b) of a heater (10) in a part facing an inner peripheral surface (137b) of a leading end part (137) of a housing (110) and interposed in a leading end side annular gap K1, so as to maintain a gap with the inner peripheral surface (137b). A decline in detection accuracy can be prevented to the extent that combustion gas can be received by the leading end (72) of the convex portion (70) even if soot clogging should occur.