PURPOSE: To prevent the failure etc. of substrates, make possible continuous treatment and improve productivity by performing the orientation treatment on both surfaces of a central part substrate in a liquid crystal display device of plural layer structure by an ion beam etching method.

CONSTITUTION: In a vacuum chambers 1, glass substrates 2 (these are glass substrates formed with display electrodes then further formed thereon with an insulation film of SiO2, TiO2, etc. and the insulation film is etched by ion beams) are moved by a belt conveyor 3. Irradiation is made from both sides of said glass substrates 2 by means of two ion beam mirrors 4, 5. The angles of irradiation are 60W90°, and ions of Ar, O2, N2, etc. are used for the irradiation ions. In the figure, a glass substrate supporting table is shown by 6. In this way, there is no need for replenishment of evaporating materials, unlike in a diagonal vapor deposition method, and continuous treatment is made possible. Since no mechanical forces are exerted to the substrates, there is no failure of the substrates and the production efficiency is enhanced.