A skin current heater for generating heat from a conductive tube by passing an insulated wire or cable through the conductive tube, feeding a current through the insulated wire or cable and generating a current flowing reversely to the current in the vicinity of the inner surface of the conductive tube. In a heat generating section for increasing the heating value, the conductive tube consists of a pair of steel tubes spaced apart from each other and a steel tube for connecting them, outer surface of the steel tube is connected electrically with the inner surface end part of the connecting steel tube, and an insulating means prevents the outer surface of the steel tube connected electrically and the outer surface of the steel tube other than the inner surface end part of the connecting steel tube from touching the inner surface of the connecting steel tube thus increasing the heating value in the heat generating section as compared with other part.
