The interfacial tension gamma of hexane solution of 1,1,2,2-tetrahydroheptadecafluorodecanol (FC10OH) against water was measured as a function of pressure p and molality m(1) at 298.15 K. The break points were observed on the gamma vs p and gamma vs m(1) curves. The interfacial density Gamma(1)(H) increases and the volume change associated with the adsorption Delta nu decreases with increasing m(1), and they change discontinuously at concentrations of the break points. By drawing the interfacial pressure pi vs area A curve, it is concluded that two types of phase transitions take place from the gaseous to the expanded state and from the expanded to the condensed one in the adsorbed film of FC10OH. By examining our results by the Clapeyron type equations, the order of phase transition was considered first. The partial molar volume change associated with the adsorption of FC10OH was estimated and compared with that of 1-octadecanol (C18OH) It was found that FC10OH molecules were accompanied with the larger decrease in partial molar volume inherent in the interface than C18OH molecules when the phase transition takes place from the expanded to the condensed state in the adsorbed film. This suggests that the microscopic circumstance in the adsorbed film affects appreciably the volume change of adsorption.