A construction machine or industrial vehicle having a power supply system which includes a chargeable and dischargeable capacitor and a feeder circuit connecting a battery and the capacitor to a load capable of power running and regeneration. The capacitor is connected through a DC/DC converter which includes a controller that controls energy charged or discharged by the capacitor through the DC/DC converter to the load. The controller includes a power running/regeneration operation estimater which estimates an operation pattern including a point of change between power running and regeneration modes of the motor, or DC current supplied to an inverter, or control lever information and previously stored operation pattern information, and a capacitor target voltage calculator which controls an output command value of the DC/DC converter according to the estimated operation pattern so that a capacitor target voltage sequentially decreases in power running and sequentially increases in regeneration.