Evolutions of the complex elastic stiffness and the Raman scattering spectrum were measured during the dehydration process of the polyacrylamide gel. The elastic-stiffness amplitude grew around 10 3 times as large as the initial value and the loss tangent reached a peak around the time when the log of the simultaneously measured weight showed a bend point (t g ′ ). Besides, in the Raman scattering experiment, a pair of broad peaks emerged in the low-frequency region around t g ′ . The results in the present study indicate that some transition like the glass transition in the non-crystalline polymers takes place around t g ′ .