Hill's plastic constitutive equation for anisotropic materials was formulated based on the coordinate system whose axis directions coincide with those of principal axes of material anisotropy. Then, it has been reported in the past that the principal axes of material anisotropy rotate by the added plastic deformation and do not coincide with those of the initial material. Thus, several models for taking into account the rotation of the principal axes of material anisotropy have been investigated. In this report, we proposed a revolution law of the rotation of the principal axes and incorporate the revolution law into the constitutive equation proposed by Goya & Ito that describes the directional dependence of the plastic strain increment on the stress increment.