PURPOSE: To improve the efficiency of ionization of a thin film forming material by regulating high frequency voltage impressed on substrates on which the material is deposited in vacuum, high frequency voltage impressed on exciting plates and DC voltage impressed on the substrates.

CONSTITUTION: A thin film forming material 5 is evaporated in a vacuum vessel 1. A first high frequency voltage and DC voltage are impressed between the material 5 and substrates 8 to make electric potential lower on the substrate 8 side. A second high frequency voltage is impressed between exciting plates 12, 15 arranged near the material 5 and the evaporated thin film forming material. The evaporated thin film forming material is ionized and deposited on the substrates 8.