To enhance the efficiency for regenerating braking energy.

This device includes an automatic transmission between an internal combustion engine and a driving system member; a braking detecting means S10 detecting the operation of a braking control member; pump operation detecting means S10, S12 detecting the pump operation (start S14 of pump control) of a hydraulic pump/motor; a fuel adjustment means S20 normally controlling the amount of fuel supplied to the internal combustion engine and stopping the fuel supply to the internal combustion engine when the operation of the braking control member is detected by the braking detecting means while the vehicle is running; and a control means S18 controlling the speed reduction ratio of the automatic transmission to minimize it when the operation of the braking control member is detected by the braking detecting means and the pump operation of the hydraulic pump/motor is detected by the pump operation detecting means while the vehicle is running.