To provide a method for producing a dielectric thin coating film capable of reducing damage to be given to a substrate or the like at the time of forming the dielectric thin coating film, capable of forming the dielectric thin coating of a high quality and furthermore easy to realize it by an ordinary plasma CVD device and to provide a producing device therefor.

A substrate S is placed on a lower electrode 14, is heated by a heater 16 while the inside of a reaction vessel 12 is held to a prescribed evacuated state and is held to a prescribed temp. A gaseous starting material obtd. by evaporation by an evaporator is mixed with gaseous O2 and is thereafter fed to a substrate S. Parallelly, a grid electrode 20 is applied with a prescribed potential, and an upper electrode 18 is applied with a high-frequency voltage, by which plasma is generated on a space between the upper electrode 18 and the grid electrode 20. Thus, the gaseous starting material is decomposed and brought to react with to accumulate the reaction product on the substrate S, by which the dielectric thin coating film can be formed.