To provide a plasma generator capable not only of improving the reaction efficiency of a photocatalyst and a target reactant but also of realizing a low cost and a photocatalytic activity control method using the plasma generator.

The provided plasma generator includes a pair of electrodes 11A and 11B configured in opposition to one another and dielectric films 12A and 12B configured respectively on mutually opposing surfaces of the electrodes 11A and 11B so as to execute a plasma discharge by impressing a specified voltage between the electrodes 11A and 11B, whereas multiple beads 14 wherein films 15 consisting of a photocatalyst are formed on the surfaces thereof are configured within a plasma discharge region 13.