IR spectra of the OH stretching vibrations of 2-naphthol-B (B=H₂O and CH₃OH) clusters in S₁ have been measured by photofragment detected IR spectroscopy (PFDIRS). In this spectroscopy, a tunable IR light pulse excites the OH stretching vibration of the electronically excited 2-naphthol-B, which is prepared by a UV light pulse. The vibrationally excitd cluster immediately predissociates to generate a 2-naphthol fragment in S₁. By monitoring the emission only form the 0⁰₀ band of the fragment with a monochromator while scanning the IR frequency, a background free IR spectrum of the OH stretching vibration of the cluster in S₁ has been successfully obtained. By comparing the IR spectra of the cluster in S₁ with those of in S₀, the effect of the electronic excitation on the frequency change of the OH stretching vibration in the cluster is discussed.