Low-frequency Raman spectra of ethanol-water mixtures as a function of concentration are measured. We reconfirm the isosbectic point at 130 cm(-1) in the chi "(nu) spectra [1]. The chi "(nu) spectra of the mixtures can be decomposed into the linear combination of pure water and neat ethanol in the frequency range from 40 to 250 cm(-1). Below 40 cm(-1), the spectra cannot be decomposed into the linear combination and systematic deviations are found. The results indicate that the microscopic aggregation of water and ethanol molecules depends on the mixing ratio.