A fine conductive film having improved transparence, good conductivity and low-cost characteristics for use on a flat Braun tube to achieve an improved operational efficiency and cost reduction effect, is made by application at room temperature of on constituent selected from the group consisting of indium chloride, indium nitride and indium sulfide, possibly supplemented by tin chloride, dissolved in water and having added to the resulting solution an organo amino silane ester, to thereby form an indium and/or tin hydrate which is then cured by gradually raising the temperature to over 390.degree. C. and up to 450.degree. C.