To provide a deposited film forming device capable of improving the uniformity in the film thickness and film properties of a deposited film, and further capable of improving the film properties of the deposited film.

In the device where a deposited film is formed on a cylindrical support by a plasma CVD (Chemical Vapor Deposition) process using: a gas introduction means composed of a plurality of gaseous starting material introduction tubes; an exhaust means performing exhaust from the side walls in a cylindrical reaction vessel; and a means of exciting a gaseous starting material by discharge energy, the exhaust directions in the circumferential direction within each gaseous starting material introduction tube and the cylindrical reaction vessel are the same number, and also, structures are not present in a region A which is the region where the circumferential direction is surrounded by the following I, II and II, and also, the axial direction corresponds to the cylindrical support: I is a straight line obtained by connecting the center of each gaseous starting material introduction tube and the center of the cylindrical support; II is a straight line obtained by connecting the center of the exhaust port closest viewed from each gaseous starting material introduction tube; and III is the inner wall of the cylindrical reaction vessel.