Stress relaxation has been measured on N-isopropylacrylamide gel around the volume phase transition point. In the swollen phase, a uniaxial stretching of the gel induces appreciable swelling, and the kinetics of stress relaxation is identical to that of swelling. In the shrunken phase, the stress relaxation is governed by shear relaxation without swelling. The drastic change in the relaxation kinetics occurs within +/-0.2 degreesC of the transition temperature. The results are analyzed in terms of the phenomenological theory of the stress effect on gels and the formal theory of elastic relaxation. Highly contrastive behaviors of the shear relaxation modulus between the two phases have been observed, which indicate that the time scale of the conformation change associated with the shear deformation is much faster in the swollen phase than in the shrunken phase. Possible mechanisms of the stress relaxation in both phases have been proposed.