NOVELTY - A thin-film formation method involves supplying film-forming gas at atmospheric pressure, to discharge space of container, and supplying air outside discharge space when required.    USE - For forming thin film such as electrode film, dielectric protective film, semiconductor film, transparent electrically conductive film, anti-reflection coating film, optical interference film, barrier film, hard coating film, undercoat film, on base material used in various electronic elements/devices such as liquid crystal display element, organic electro luminescent element, plasma display panel, electronic paper, touch panel, solar cell, semiconductor device, and recording device.    ADVANTAGE - Enables easily and cheaply producing the thin film, by supplying gas at atmospheric pressure, to the discharge space, and supplying air for performing oxidative treatment of the base material, outside the discharge space.    DETAILED DESCRIPTION - A gas supplied at atmospheric pressure or pressure which is near atmospheric pressure, to discharge space formed in reaction container, between counter electrodes, is excited by applying high-frequency voltage to discharge space. Base material (F) is exposed to excited gas, for forming thin film on base material. Air is supplied outside discharge space of container, between consecutive film-forming operations. Air discharge pipes (37) discharge air in the portion of the container, which is outside the discharge space. Exhaust port (53) exhausts gas used for thin-film formation, from the container, at a higher flow rate than the supply rate of gas to the container. The air contains 3-20 volume% of oxygen. Frequency of the high-frequency voltage is 200 KHz or more, and 150 MHz or less. Output of the high-frequency voltage is more than 1 W/cm2, and below 50 W/cm2. The gas consists of hydrogen, methane, or water vapor, and contains an organometallic compound.    INDEPENDENT CLAIMS are included for the following:    (1) thin film comprising a transparent, electrically conductive film; and    (2) atmospheric-pressure type plasma processing apparatus in which film-formation gas is supplied to discharge space, at atmospheric pressure.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of atmospheric-pressure plasma processing apparatus.    air discharge pipes (37)    gas supply unit (50)    exhaust port (53)    air supply unit (55)    base material (F)