A plating processing method of a gripping surface of a gripping tool includes: temporarily and evenly fixing a plurality of first diamond grains having a uniform first grain diameter; adhering the first diamond grains by depositing a metal containing nickel on a gripping surface in a uniform thickness after the first diamond grains have been temporarily fixed; placing a plurality of second diamond grains having a second grain diameter on a metal surface of the gripping surface on which first diamond grains are not present; and adhering the second diamond grains by further depositing a metal containing nickel within a second plating solution on the metal surface in a uniform thickness that does not exceed the first diameter grain and the second diameter grain until a position relationship between the metal surface and the second diamond grains is not displaced even when the gripping tool is moved.