Isothermal vapor-liquid equilibrium measurements were performed for the 2-propanol + water system containing poly(ethylene glycol) (PEG) at 298.15 K by a dow type apparatus. Three different PEGs whose molecular weights are 200, 1000, and 20 000 were employed, and their mass fractions in the liquid phase were up to 0.35. The volatility of water was reduced by the addition of PEG, and the azeotropic point of the 2-propanol + water system was changed to a higher mole fraction of 2-propanol. Activity coefficients of solvent were calculated by assuming the monodispersity of PEG. It was found that the activity coefficients of water were selectively decreased by the addition of PEG. These phenomena did not depend on the molecular weight of PEG.