The elastopasticity behavior of a high-strength steel sheet was investigated by performing biaxial tension experiments. To evaluate the accuracy of constitutive models in describing such elastoplasticity behavior, numerical simulations of stress-strain responses were conducted for the same stress paths as those in the experiments using two types of models: the isotropic hardening model (IH model) and the kinematic hardening model proposed by the present authors (Yoshida-Uemori model). In this work, special emphasise is placed in the cases of stress-path change. In experiments on radial loadings after equibalanced tension preloading, it was found that flow stresses are considerably lower than uniaxial tension flow stress. The IH model hardly describes this phenomenon, although it is sufficient for stress-strain analysis of proportional loading cases. In contrast, the Yoshida-Uemori model can well predict every stress-strain response in biaxial stress-path changes.