OH stretching vibrations of 2-naphthol-(H₂O)_n (n=0-3 and 5) hydrogen-bonded clusters in the S₀ state have been observed by infrared-ultraviolet (IR-UV) double-resonance spectroscopy. In bare 2-naphthol, cis- and trans-isomers were identified by the comparison of the observed OH frequencies with those obtained by ab initio calculations with the HF/6-31G basis set. The OH stretching vibrations (ν_OH) of hydrogen-bonded 2-naphthol-(H₂O)_n show characteristic shifts depending on the cluster size. They are classified into hydrogen-bonded ν_OH, and ν_OH free from the hydrogen bond. The cluster structures were also examined by comparing the observed IR spectra with simulated ones. It was found that the clusters with n=2 and 3 form ring structures, while the cluster with n=5 exhibits an ice (I) structure.