An active gas generation apparatus (51, 52, 53) configured to generate an active gas obtained by activating a source gas supplied to a discharge space (61, 62, 63), the active gas generation apparatus comprising: a first electrode component; and a second electrode component (2, 2X, 2Y) provided to face said first electrode component, wherein said first electrode component includes a first electrode conductive film (10, 10A, 10B), said second electrode component includes a second electrode conductive film, wherein the discharge space includes a region where said first and said second electrode conductive films overlap in a plan view, wherein the discharge space exists in a main dielectric space where said first and said second electrode components face each other, and wherein, in use, an AC voltage is applied in the discharge space between said first and said second electrode conductive films, wherein said first electrode component further includes a first electrode main dielectric film provided, on a side of said discharge space (61, 62, 63) with respect to said first electrode conductive film, adjacent to said first electrode conductive film, and a first additional electrode dielectric film provided, on a side of said discharge space (61, 62, 63) with respect to said first electrode main dielectric film, at a first distance with respect to said first electrode main dielectric film, wherein a first additional dielectric space is provided between said first electrode main dielectric film and said first electrode additional dielectric film, said main dielectric space is provided between said first electrode additional dielectric film and said second electrode component (2, 2X, 2Y), said first additional dielectric space is set such that, in use, a dielectric barrier discharge is not caused in said first additional dielectric space when a dielectric barrier discharge is caused in said discharge space (61, 62, 63) in said main dielectric space, said first electrode main dielectric film includes said first electrode conductive film (10, 10A, 10B) in a plan view, and has a formation area larger than said first electrode conductive film, and said first electrode additional dielectric film includes said first electrode conductive film (10, 10A, 10B) in a plan view, and has a formation area larger than said first electrode conductive film and smaller than said first electrode main dielectric film. a first electrode component; and a second electrode component (2, 2X, 2Y) provided to face said first electrode component, wherein said first electrode component includes a first electrode conductive film (10, 10A, 10B), said second electrode component includes a second electrode conductive film, wherein the discharge space includes a region where said first and said second electrode conductive films overlap in a plan view, wherein the discharge space exists in a main dielectric space where said first and said second electrode components face each other, and wherein, in use, an AC voltage is applied in the discharge space between said first and said second electrode conductive films, wherein said first electrode component further includes a first electrode main dielectric film provided, on a side of said discharge space (61, 62, 63) with respect to said first electrode conductive film, adjacent to said first electrode conductive film, and a first additional electrode dielectric film provided, on a side of said discharge space (61, 62, 63) with respect to said first electrode main dielectric film, at a first distance with respect to said first electrode main dielectric film, a first electrode main dielectric film provided, on a side of said discharge space (61, 62, 63) with respect to said first electrode conductive film, adjacent to said first electrode conductive film, and a first additional electrode dielectric film provided, on a side of said discharge space (61, 62, 63) with respect to said first electrode main dielectric film, at a first distance with respect to said first electrode main dielectric film, wherein a first additional dielectric space is provided between said first electrode main dielectric film and said first electrode additional dielectric film, said main dielectric space is provided between said first electrode additional dielectric film and said second electrode component (2, 2X, 2Y), said first additional dielectric space is set such that, in use, a dielectric barrier discharge is not caused in said first additional dielectric space when a dielectric barrier discharge is caused in said discharge space (61, 62, 63) in said main dielectric space, said first electrode main dielectric film includes said first electrode conductive film (10, 10A, 10B) in a plan view, and has a formation area larger than said first electrode conductive film, and said first electrode additional dielectric film includes said first electrode conductive film (10, 10A, 10B) in a plan view, and has a formation area larger than said first electrode conductive film and smaller than said first electrode main dielectric film.