PURPOSE: To finish the tip surface of a minute hole preventing the rounding of the edge of the hole, by boring a minute hole to a material, planting the surface with a metal soluble in an acid and having similar hardness to the material, polishing the tip surface of the hole, and dissolving and removing the metal with an acid.

CONSTITUTION: A spinning nozzle 6 is bored to a spinneret plate 5, and the whole surface is plated with Ni by electroplating to form an Ni layer of 1μ thick. The surface is further coated with a Cu layer of several tens μ thick by electroplating. The outer surface of the spinneret plate 5 is polished with a buff to remove the Ni layer 7 and the Cu layer 8 from the outer surface. Thereafter, the Ni layer 7 and the Cu layer 8 in the nozzle 6 are dissolved and removed with nitric acid, and the spinneret is washed and dried.