Provided in an active gas generation apparatus according to the present disclosure is a gas separation structure of separating a gas flow between an in-housing space and a discharge space by a cooling plate, an electrode holding member, and a high voltage apply electrode part. The active gas generation apparatus further includes an auxiliary metal electrode provided on an upper surface of an electrode dielectric film in the high voltage apply electrode part. The auxiliary metal electrode is provided to overlap with part of an active gas transmission path in a plan view, and set to ground potential.