The adsorption isotherms of H2O, CH3OH, and C2H5OH on fluorinated activated carbon fiber (F-ACF) and pristine ACF were measured. H2O was not adsorbed by F-ACF, while the H2O adsorption isotherm of ACF was of type V. The adsorption isotherms of CH3OH and C2H5OH by ACF were of type I. On the other hand, their isotherms by F-ACF were of type V. In particular, the uptake in low pressure regions was markedly decreased by fluorination.