To prevent a battery from being deteriorated and prevent the operation of a small-sized apparatus, to which power is supplied, from being unstable, in a power system provided with a generator as a power supply and the battery.

The apparatus to which the power is supplied is divided into a plurality of groups. A charge/discharge control section 22 obtains the suppliable power amount of the power supply (generator 11 and battery) based on the charge/discharge condition of the battery 12. An operation command including an operating state of each mounted apparatus and operating information that indicates whether the generator is in operation or not is given to the charge/discharge control section 22, and the charge /discharge control section 22 obtains necessary power consumption based on the operation command, to determine the order of priority of the groups. When the power consumption is larger than the suppliable power amount, a power control device (control- arithmetic unit 24 and power control section 25 or 28) controls a power supply every group in accordance with the order of the priority.