Abstract: A method of manufacturing a chemically adsorbed film, which can efficiently provide a water and oil repelling and anti-contaminating ultra thin film with uniform thickness by spraying a solution comprising a chemical adsorbent on a substrate surface having active hydrogen groups in a dry atmosphere. A chemically adsorbed film can be formed by spraying a chlorosilane-based surface active agent on a substrate surface having active hydrogen groups such as hydroxyl, imino groups or the like. After forming a siloxane-based monomolecular layer or polysiloxane layer beforehand by spraying a chlorosilane compound or a solution comprising a chlorosilane compound on a substrate surface, a chemically adsorbed monomolecular or polymer layer can be formed by spraying a solution comprising a chlorosilane-based surface active agent. The film can be formed in a short time without being inhibited by the shapes and sizes of substrates.