A glow plug includes a heater member; heater power lead wires which extend rearward along an axis and whose conductors electrically communicate with one and of a heater conductor for supply of power; a sensor, portion for detecting the combustion pressure of an internal combustion engine; a sensor connection line connected to the sensor portion and extending rearward along the axis; a housing; a sensor-portion-enclosing tube; and a grommet formed from an insulating rubber-like elastic material., having insertion holes through which the heater power lead wires and the sensor connection line are respectively inserted, the grommet liquid-tightly closing an end portion of the sensor-portion-enclosing tube and liquid-tightly holding the heater power lead wires and the sensor connection line.