Finishing agents comprise the combination of alkoxysilane surface active agent, silanol condensing catalyst, and nonaqueous liquid or solid medium, or the combination of alkoxysilane surface active agent, acid catalyst and liquid or solid medium. In the latter embodiment, it is preferred that at least one of the alkoxysilane surface active agent and the acid catalyst be microencapsuled. The finishing agent permits formation of chemically adsorbed protecting films. Such protecting films are used for substrates of such equipments as electronics products, electric domestic products, automobile, industrial equipments, mirrors, lenses for glasses and the like. The protecting films have a durability and heat, weather and abrasion resistance, and also water and oil repellent properties.