PURPOSE: To simply form conductive layers by forming preparatory conductive film on glass conductive material layers on the glass surface by the ion plating process using this preparatory conductive film as an electrode, and removing the preparatory conductive film.

CONSTITUTION: After the preparatory conductive film 5, such as aluminum is formed on the convex surface 2 of the meniscus lens 1, indium is coated by projecting the indium ion flow 10 on the meniscus lens 1 under the inert atmosphere, such as argon. Then, the indium is chemically treated on the ion-plated meniscus lens 1 and the preparatory conductive film 5 is melted and removed. Since the indium driven on the convex surface exists in the glass organization, it is not affected directly by this chemical treatment.