Infrared spectra of fluorobenzene-(CH₃OH)_n (n = 1 and 2) clusters in their ground state were observed in the OH and CH stretching vibrational region. The sizes and structures of the clusters were examined. As a result, the size dependence of the intracluster nucleophilic substitution reactions accompanied with ionization were confirmed. We also found the isomer dependence of the reactivity in fluorobenzene-(CH₃OH)₂. The OH stretching vibrations in the electronic excited state (S₁) were also observed. No significant structural change in the electronic excitation was confirmed.