It is required that a line width of a wiring is prevented from being wider to be miniaturized when the wiring or the like is formed by a dropping method typified by an ink-jetting method. Toner images of different colors are sequentially transferred from the image carriers to a sheet being conveyed by an endless belt while electrostatically adhering to the belt, completing a color toner image. The conical section is centered with respect to a center axis and extends from the center axis towards the outer edge. The instrument is adapted for coupling to a high frequency power supply or electrosurgical generator. The safety is triggered by this output from the optical fiber sensor.