We found that the Raman-Stokes shift of the C=N stretching mode of Phenol Blue changes with excitation energy; the frequency of this Raman band increased with an increase of the excitation energy, whereas the bandwidth was almost the same. The origin of the excitation energy dependence is discussed in connection with the correlation of the effect of the solvent fluctuation on the electronic transition energy and the vibrational frequency. (C) 1997 American Institute of Physics.