PURPOSE: To form a metallic thin film which has a small uptake of impurities in the film by forming the thin film by repeating such a sequence that a next gaseous starting material is supplied after a gaseous starting material adsorbed to the surface of a substrate is completely consumed through a surface reaction.

CONSTITUTION: A substrate 7 is maintained at a desired temperature by using a heating device provided on the rear surface of a substrate supporting table 5. Then a WF6 and SiH4 gases are respectively stored in gas reservoirs under prescribed pressures by controlling the original pressures of the gases. The storing pressure of the WF6 and SiH4 gases are controlled by opening/closing air pressure valves in an interlocking way with an electromagnetic valve. Then, the WF6 and SiH4 gases are alternately supplied to the substrate 7 by controlling the opening/closing timing of electromagnetic valves 10 and 13. Therefore, a W film containing a small amount of impurities is uniformly formed on the substrate 7.