Abstract: A heating element consisting of a metal pipe, an electric resistance conductor inserted into the metal pipe and a heat resistant insulating material filled between said metal pipe and said electric resistance conductor, characterized in that said heat resistant insulating material is one obtained by coating a first insulating material such as particulate fused magnesia with a second insulating material having a lower melting temperature than that of the first insulating material such as a silicone resin, which has been molten, can maintain an insulation resistance of at least 10.sup.3 M.OMEGA. in an atmosphere at 40.degree. C and a relative humidity of 90%.