The volume phase transition is studied in the ternary system of the nonionic poly (N-normalpropylacrylamide) gel, water, and various alcohol. The gel shows a reentrant volume phase transition in all mixed solvent systems studied here. It is found that the phase transition is multiple in the mixed solvent systems of water-1-propanol and water-2-propanol. These results are discussed by the mean field theory in which the effects of the chain stiffening due to the adsorption of the solvent molecules are taken into account. These results strongly suggest that the adsorption and/or the desorption of the solvent molecules promote the multiple phase transition of the nonionic poly (N-normalpropylacrylamide) gel.