A reference voltage value is calculated by using a current value, a voltage value, and an internal resistance value of an electric storage apparatus. A dischargeable electric power is calculated by using the reference voltage value and a predetermined internal resistance value previously set to be higher than the internal resistance value. The dischargeable electric power is set as an allowable discharge electric power when temporarily increasing the discharge electric power required of the electric storage apparatus. The reference voltage value is calculated from the internal resistance value and is a fixed value regardless of the relationship between the current value and the voltage value. The dischargeable electric power is also constant. Since the predetermined internal resistance value is higher than the internal resistance value, the dischargeable electric power can be set while the deterioration of the electric storage apparatus is taken into account.