A rotary electric machine (1) which constitutes a prime bar of a vehicle and an electricity storage device (10) serving as a main power source of the rotary electric machine (1) and composed of a plurality of capacitor modules (11) in which a plurality of capacitor cells make one set are provided. A hybrid control unit (3) which comprises a means for calculating assigned voltages of the capacitor modules, a means for calculating an average value of the assigned voltages of the capacitor module, and a means for equalizing the assigned voltages of the capacitor modules based on the average value. By restricting a difference among the assigned voltages of the capacitor modules (11), it is possible to fully utilize a capacity of the electricity storage device (10).