To suppress the blur of a coating material and the dispersion in coating quantity at a time of the formation of a coating sample by bending an auxiliary tool body so as to form a coating material sump intercepting the coating material over a constant width between the auxiliary tool body and bar coater to arrange the auxiliary tool body in the contact state with the side surface becoming the moving side of the bar coater.

A flat plate member formed by using vulcanized fibers as a material is cut into a short striplike shape having a width being 1.0-2.0 times the diameter of a bar coater 3 to form an auxiliary tool body 10 and this auxiliary tool main body 10 is bent into an almost U-shape so as to form a coating material sump 20 capable of intercepting the coating material over a constant width. The auxiliary tool body 10 and the bar coater 3 are placed on a protective film 6 and a necessary amt. of the coating material is preliminarily dripped on the area between the auxiliary tool body 10 and the bar coater 3 and, subsequently, both end parts of the auxiliary tool body 10 are pressed by the thumbs of both hands while holding both ends of the bar coater 3 and drawn on this side while applying equal force to the whole of the bar coater 3 without being rotated to perform coating.