Maximum charging power of a battery (63) is set by a battery-charging power setting unit (75), while maximum discharging power of the battery (63) is set by a battery-discharging power setting unit (76). Lower and upper limit of generator output power is set by a generator output power setting unit (77). A generator/battery power distribution determining unit (81) distributes power between the battery (63) and the generator (62) using the set values above.