Swelling of polymer hydrogels is measured as a function of time using a newly designed sample cell attached to Thermomechanical analysis (TMA). In order to examine the performance of the TMA sample holder, Ca alginate dry film was used as a sample and measurement conditions of dynamic swelling of water were examined. Swelling ratio under various loading conditions was observed as a function of time. A master curve was obtained using zero loading conditions using extrapolated values of dynamic data obtained under various loadings. Swelling ratio measured by TMA at equilibrium condition accords well with swelling ratio obtained by static measurement.