The adsorption behavior of 4-cyanobenzoic acid (4CBA) on a silver film has been investigated by infrared and Raman spectroscopies. The Langmuir adsorption model was applicable not only to the self-assembling but also to the spin-coating processes. By taking the infrared reflection-absorption and surface-enhanced Raman (SER) spectra simultaneously, the 4CBA molecule was concluded to adsorb onto the film as 4-cyanobenzoate with its two oxygen atoms bound symmetrically to the surface, assuming a perpendicular orientation with respect to the surface. From the peak shift and band broadening analysis of the SER spectrum of 4CBA taken in an aqueous silver sol, on the sol surface, however, the molecule appeared to be bound via both the carboxylate and nitrile groups, assuming a flat orientation on the surface. Although the origin of such a different adsorption mechanism could not be clarified, it was tentatively ascribed to the different surface morphology.