The lattice vibrational spectra and d d electron transition spectra of the Cu∶KNSBN are compared with that of the KNSBN. The differences in the Raman spectra are little for the symmetry species A 1(z) and are very great for the symmetry species E(xy); but in the infrared reflectivity spectra, the differences are great for both A 1(z) and E(xy). It is considered that the lattice sites A and C are partly occupied by the Cu 2+ doped. The d d electron transition spectra in the visible range show that the two deep energy levels of 2.50 eV and 2.64 eV are formed by the Cu2+.