Cu(InxGa1-x)(2)Se-3.5 thin films were fabricated by rf sputtering from CuInxGa1-xSe2 and Na mixture target by controlling the mixture ratio. X-ray diffraction analyses show that the structure of Cu(InxGa1-x)(2)Se-3.5 thin films is different from chalcopyrite structure: especially, CuIn2Se3.5 thin films have a defect chalcopyrite structure. The lattice parameters for Cu(InxGa1-x)(2)Se-3.5 thin film are slightly smaller than those for CuInxGa1-xSe2 thin film and linearly decreased with increasing Ga content. The optical absorption coefficients for Cu(InxGa1-x)(2)Se-3.5 thin films exceed 2 x 10(4) cm(-1) in energy region above the fundamental band edge. The band gap for Cu(InxGa1-x)(2)Se-3.5 thin films is larger than that for CuInxGa1-xSe2 with the same Ga content and increased with increasing Ga content.