PURPOSE: To provide a title apparatus which enables film formation with a high film thickness distribution (within ±10%) even with a large area substrate.

CONSTITUTION: In a plasma CVD apparatus of parallel flat plate type which comprises a reaction chamber provided for thin film formation upon introduction of a material gas, a substrate holder 30 installed in this reaction chamber to mount a treatment substrate 20, and an electrode plate 40 counterposed to this substrate holder 30 and provided with a plurality of gas introduction ports 41 on the holder side, and which sprays the material gas from the gas introduction port 41 of the electrode plate 40 to the substrate 20 side and causes discharge between the electrode plate 40 and the substrate holder 30 to deposit a thin film on the treatment substrate 20, the periphery of the gas introduction port of the electrode plate 40 is coated with an insulator 42.