Saccharide-induced volume phase transition of poly(N-isopropylacrylamide) (NIPA) gels was found fur glucose, galactose, and sucrose, and the transition concentrations were about 1.5, 1.3, and 1.2 M, respectively. Temperature-induced volume phase transition of NIPA gels was affected by these saccharide, and the transition temperature decreased with increasing concentration of the saccharides. The reduced extent of the transition temperature increased linearly with the decrement of the chemical potential of water molecules due to the saccharides. This indicates that the change of the chemical potential of water induced by the addition of the saccharide plays an essential role in the saccharide-induced volume phase transition of NIPA gels.