A heating element (12) made of metal wire is installed at an internal circumferential surface of a cylindrical main thermal insulation body (11) of an electric heater according to the present invention. The heating element (12) comprises a plurality of resistance heat emitting portions (61)-(64) (71)-(74) (81)-(84) as segments along its length direction. The resistance heat emitting portions (61)-(64) (71)-(74) (81)-(84) are connected in parallel.