PURPOSE: To improve the precision of the size of a nozzle by generating an air flow in the nozzle, to which a hole is bored, when a surface treatment is sprayed against a nozzle plate for ink jet recording and a surface treating layer is formed to the nozzle plate.

CONSTITUTION: When an O ring 8 is placed on a nozzle plate 9 and a decompression pump 6 is driven, a nozzle plate 10 is drawn to the upper surface of a mount 1, the O ring 8 is compressed and the intrusion of air from the periphery to a decompression chamber 2 is prevented, and an air flow 12 is generated through a nozzle 11 to the decompression chamber 2 from the inside of atmospheric air. When a surface treatment 13 is sprayed on the nozzle plate 10 by the spray gun 9 under the state, a surface treating layer 14 is shaped on the surface of the nozzle plate 10, the surface treatment 13 adhering on the wall surface of the nozzle 11 is blown off or carried away in the direction of flow of the air flow 12, and the thin uniform surface treating layer 14 can be formed on the wall surface of the nozzle 11. Accordingly, the surface treating layer 14 can thinly be shaped on the whole surface uniformly on the wall surface of the nozzle 11, thus maintaining the dimensional accuray of the nozzle 11.