PURPOSE: To obtain a heating material electrode having a high resolving power and a long service life and capable of operating with lesser electric power by arranging plural heating materials whose facing side cross sections are formed into an almost circular or oblongly curved shape in parallel on an insulating base plate.

CONSTITUTION: Heating materials 2 having a circular or oblong cross section are closely arranged and wound around an insulating base plate 1 having a supporting portion 1a whose tip is pointed. The preferred number of the heating materials of a size of 25 microns or less is tens or more per 1mm even when taking into account the width of an insulating coat 3. The curvature radius R of the supporting portion 1a may be equalized with the wire diameter of the heating material 2 and the vertical length of the portion in contact with a heat- sensitive paper becomes about 2R. Thus, the number of the heating materials becomes the magnitude of about tens per 1mm.