A glow plug including a center pole extending along an axial direction; a heater including a heating element capable of generating heat upon energization, which heater is connected to a leading end portion of the center pole so as to constitute together with the center pole an integrated heater/center pole member in a mechanically rigid state; a metal shell as defined herein; and a vibration preventing member for preventing vibration of the center pole, the vibration preventing member being fixed on an outer peripheral surface of the center pole at an axial position corresponding to a portion where an inside diameter of the axial hole of the metal shell is constant.