Abstract: In a method of and an apparatus for forming a thin film on a substrate, a rotary electrode is provided and rotated so that an electrode surface of the electrode moves and passes by a substrate surface due to the rotation of the electrode. Thereby a reaction gas is supplied into a gap between the substrate surface and the electrode surface. A high-frequency power is applied or dc power to the rotary electrode thereby generating a plasma between the substrate surface and the electrode surface, for forming the thin film by chemical reaction of the reaction gas supplied into the plasma.