To provide a method for forming a film of high quality in high productivity in which a vapor depositing material is held in a state of high purity without oxidizing it.

Arc discharge is executed with a cathode 15 and an Al cathode 16 for arc discharge in a guiding part in a vacuum atmosphere and an anode 17 arranged oppositely thereto, an Al ion 19 is guided to a substrate 21 by an electromagnetic coil 18, and the Al ion 19 is brought to react with oxygen fed from an oxygen feed tube 13 in the vicinity of this substrate 21, which is vapor-deposited on the substrate 21 to form an Al2O3 film.