PURPOSE: To enable equalized formation of an antistatic film on the inner wall of a vacuum cylinder by coating the outer surface of a core material, which is worked so that it has the same shape as the internal shape of the vacuum cylinder, with a conductive film, and dissolving and removing the core material after an insulating member is attached on the conductive film.

CONSTITUTION: After a core material 1 is subjected to machine work according to the internal shape of a vacuum cylinder, the outer surface of the material 1 is homogeneously coated with a conductive film 2 made of gold, platinum or the like. An insulating member 3 made of a synthetic resin is attached to the outer surface of the film 2, and the member 3 is subjected to machine work according to a desired external shape of the vacuum cylinder. Following that, the material 1 is dissolved and removed with hydrochloric acid or the like, after it is cut so that the etching is facilitated. By the means mentioned above, the film 2 with antistatic property, which is formed on the inner wall of the vacuum cylinder, can be formed from the outer surface and not from the inner surface of the vacuum cylinder. Consequently, the thickness of the film 2 can be equalized, and the electron beam can be stabilized.