A vacuum apparatus comprising: a vacuum chamber; a RF source; a matching box having a variable inductance element for electrically controlling impedance; a plasma generator, connected to said RF source via said matching box, for generating plasma by RF voltage outputted from said RF source, an ionization chamber; a gas supply system for supplying gas to said ionization chamber; a coil wound around said ionization chamber, the plasma being generated by an alternating current field formed by alternating current flowing through said coil; a first electrode disposed in an opening of said ionization chamber and a second electrode disposed farther from said ionization chamber than said first electrode; a voltage supply for applying a positive voltage to the first electrode and a negative voltage to the second electrode, to extract positive ions from said plasma by the electric field between said first and second electrodes (45, 46), in order to release the positive ions into said vacuum chamber; an electron generator for releasing electrons into said vacuum chamber in order to neutralize a flow of said positive ions by applying said electrons; wherein said plasma generator is an ion gun, and wherein the vacuum apparatus is adapted to subject a target object disposed in said vacuum chamber to vacuum processing by irradiating positive ions neutralized by said electrons to the target object; and when plasma is regenerated due to disappearance of said plasma, to apply a voltage higher than that of said vacuum chamber to said second electrode, in order to attract said electrons emitted from said electron generator to said ionization chamber. a vacuum chamber; a RF source; a matching box having a variable inductance element for electrically controlling impedance; a plasma generator, connected to said RF source via said matching box, for generating plasma by RF voltage outputted from said RF source, an ionization chamber; a gas supply system for supplying gas to said ionization chamber; a coil wound around said ionization chamber, the plasma being generated by an alternating current field formed by alternating current flowing through said coil; a first electrode disposed in an opening of said ionization chamber and a second electrode disposed farther from said ionization chamber than said first electrode; a voltage supply for applying a positive voltage to the first electrode and a negative voltage to the second electrode, to extract positive ions from said plasma by the electric field between said first and second electrodes (45, 46), in order to release the positive ions into said vacuum chamber; an electron generator for releasing electrons into said vacuum chamber in order to neutralize a flow of said positive ions by applying said electrons; wherein said plasma generator is an ion gun, and wherein the vacuum apparatus is adapted to subject a target object disposed in said vacuum chamber to vacuum processing by irradiating positive ions neutralized by said electrons to the target object; and when plasma is regenerated due to disappearance of said plasma, to apply a voltage higher than that of said vacuum chamber to said second electrode, in order to attract said electrons emitted from said electron generator to said ionization chamber.