PURPOSE: To provide a heating device which can maintain the insulation, gives no fear of electric shock and can safely stop the power feeding function even in the final period of the service life of a heating body.

CONSTITUTION: This heating device 4 is composed of a sheath heater 1 to be a heating body to heat a liquid; a water pipe 2 to pass the liquid; and a heat conductive metal part 3 to integrally connect the heating body 1 and the water pipe 2. The water pipe 2 is formed of an electric insulating material, and furthermore, this heating device 4 is installed to the other structure of an apparatus by electrically insulating through an electric insulator.