PURPOSE: To check the damage, the abrasion condition, etc., of an abrasive material layer by sight easily and accurately and to make it possible to do the required polishing for a smooth surface at all times by dividing the abrasive material layer by coloring concentrically into several layers of the same thickness and different color.

CONSTITUTION: This is a buff for polishing a printed wiring board 6 having an abrasive material layer 5 that is made by winding and laminating, for example, blue-colored nonwoven cloth layers 5a and yellow-colored nonwoven cloth layers 5b, both in nearly the same thickness, alternately and concentrically. When the required polishing for a smooth surface is conducted by rotating and sliding the buff for polishing 6, the surface of a primary slide region 6a is worn away with the progress of the polishing and then another new colored surface 5a is exposed. According to the kind and position of the newly exposed colored layer 5a, the degree of abrasion and damage condition of the abrasive material 5 can be known visually even in the polishing work for a smooth surface. Without interrupting the polishing for a smooth surface, therefore, it is easily decided whether any fine adjustments are required for the polishing pressure condition.