A planar heating element has an electrical insulating substrate, at least one pair of electrodes that includes thin metal wires covered with conductive cover layers and that is placed on a surface of the electrical insulating substrate, a polymer resistor that is placed on the electrical insulating substrate and that is supplied with electricity from the electrodes, and electrical insulating cover material 16 that covers the electrodes and the polymer resistor and that is made to adhere to the electrical insulating substrate by hot melt, and sectional shape of the conductive cover layers is of an ellipse in general with long axis parallel to the surface of the electrical insulating substrate.