Aluminum alloy sheet metals have been widely utilized for a light weight construction of automobile. However, Aluminum sheet metals still remain one of the difficult materials to predict the accurate final shapes after press forming processes, because of several mechanical weak features such as lower Young's modulus, strong plastic anisotropy of yield stress, Lankford values, and so on. In order to solve the problems, the present author has developed a new constitutive model called "Modified Yoshida-Uemori model". The present model can describe accurate non-proportional hardening behaviors of Aluminum alloy sheet metals. In the present research, several experimental procedures were carried out to reveal the mechanical properties of Aluminum alloy sheet metals. From the comparison between experimental data and the corresponding calculated results by our constitutive model, the performance of our model was evaluated. In addition to the above mentioned research, the evaluation of some springback analyses were also carried out. The calculated results show good agreements with the corresponding experimental data.