A battery model unit includes an electrode reaction model unit based on the Butler_Volmer equation, an electrolyte lithium concentration distribution model unit analyzing a lithium ion concentration distribution in an electrolyte solution by a diffusion equation, an active material lithium concentration distribution model unit analyzing an ion concentration distribution in a solid state of an active material by a diffusion equation, a current/potential distribution model unit for obtaining a potential distribution according to the charge conservation law, a thermal diffusion model unit and a boundary condition setting unit. The boundary condition setting unit (66) sets a boundary condition at an electrode interface such that a reacting weight at the electrode interface is not determined by a difference in material concentration between positions but a deviation from an electrochemically balanced state causes a change with time in lithium concentration at the interface and thus a (time-based) drive power for material transportation. Thereby, an appropriate charge/discharge control can be performed based on the battery model having the appropriately set battery condition.