A heating device is presented for surface heating of a body so as to maintain a required temperature of the body. The heating device comprises an electrical heating element and a power source for supplying a required voltage thereto. The heating element comprises first and second conductors, wherein the first conductor is made of a material with relatively high specific resistivity as compared to that of the second conductor, and the second conductor is made of a material with high heat conductivity. The first and second conductors are accommodated in spaced-apart parallel relationship along their lengths such that, when they are connected to the power source, electric currents flow in the conductors in opposite directions, and magnetic fields created in the vicinity of the first and second conductors are completely compensated. The first conductor thus serves as a heater and the second conductor as a heat diffuser. By accommodating the heating device such that it faces the body by the second conductor, as low as desired temperature gradient between the surface temperature of the heating conductor and the required temperature of the body can be obtained.