Creep deformation occurs in ductile metals without cracks. Hence, the conditions of equilibrium and continuity of displacement are satisfied throughout the polycrystal. A method satisfying both of these conditions to calculate the macroscopic polycrystal stress-strain-time relation from that of the component crystals has been developed. Mechanical equation of state has been shown to represent approximately the polycrystal creep behavior under tensile loadings. The tensile strain E 1 1 C is taken as a function of the tensile stress T 1 1 and the current amount of tensile creep E 1 1 C . This is expressed as E 1 1 C = F(T 1 1 ,E 1 1 C ), where F is a function. It has been found that a stress-strain-time relation satisfying the mechanical equation of state in the component crystals gives a macroscopic polycrystal stress-strain-time relation that also satisfies the mechanical equation of state. In this study, we assume the creep strain in a slip system of a component crystal to have a similar equation γ m C = (τ m ,γ n C ' s), where γ m C is the creep strain in the mth slip system, γ n C 's cover all the slid systems, τ m is the resolved shear stress in the mth slip system, and is a function. This component crystal creep behavior is derived from polycrystal creep test under a nonradial loading. Then this derived component crystal creep characteristics is used to calculate the polycrystal stress-strain-time curves of two other nonradial loadings. These calculated curves agree with the experimental results much better than those found from the commonly used von Mises' theory.