The OH stretching vibration of jet-cooled phenol-N-2 in the neural and cationic ground states was observed by using infrared-ultraviolet double resonance spectroscopy and infrared photodissociation spectroscopy, respectively. The OH vibration showed a small but significant low-frequency shift of 5 cm(-1) upon the cluster formation in the neutral, while the shift drastically increased up to 159 cm(-1) in the cation. These results represent the direct evidence of the in-plane cluster structure, in which phenolic OH is hydrogen bonded to N-2, as was proposed in the zero kinetic energy photoelectron study [S. R. Haines et al., J. Chem. Phys. 109, 9244 (1998)].