The ability to reduce palladium (Pd) ions to Pd nanoparticles has been provided on the surface of cycloolefin polymer (COP). The origin of this reductive function is aldehyde and alcoholic hydroxy groups formed by oxidizing the COP surface with active oxygen species, which were generated through the irradiation of atmospheric oxygen and water molecules with vacuum ultraviolet light of 172 nm in wavelength. The Pd nanoparticles successfully served as catalysts for electroless plating.