The viscosity of an electrorheological fluid (ER fluid) increases with an increase in the intensity of an electric field. In the case of ER fluid-assisted micro polishing the workpiece needs to be a conductive material such as tungsten carbide and the gap between the workpiece and the polishing tool, which both act as electrodes, must be the same size as the abrasive grain. It is difficult to maintain a small gap when polishing the surface of the workpiece. In order to prevent direct contact between the workpiece and the polishing tool, a resin-coated polishing tool has been developed. In this paper, a micro polishing tool was made using a plasma chemical vapor deposition method. The geometry of the polishing tool was examined by a finite element method (FEM) to optimize the concentration of the abrasive grains. In polishing machining using the tool, the width of the polishing groove was 35 μm, and polishing machining in a micro area was achieved.