PURPOSE: To prolong the service life of a break device by generating a brake power due to power generation in the operation of break device, by installing a power generator in a power transmission mechanism set between the output shaft of a transmission and the driving wheel of a vehicle, and driving the power generator to generate power when stepping on a break pedal is detected.

CONSTITUTION: A transmission 2 is connected contiguously to an engine 1, and a driving power is transmitted to a driving wheel 5 from the output shaft 10 of the transmission 2 through a connecting shaft 3 and a differential gear 4. A power generator 11 is interposed in such a power transmission mechanism. Further, an always opened limit switch 12 is installed as a brake pedal stepping-ON detection means, and a resistance 13 as load is connected in series with the limit switch 12, and a closed circuit is constituted with the power generator 11. When a brake pedal 6 is stepped on, and brake oil is supplied into the left and right brake devices 9, and the torque of a rotary shaft 8 is to be cut off, power generation action is performed by the power generator 11, having the resistance 3 as a load, by closing the limit switch 12 at the same time, and the brake power due to power generation is applied to the driving power of a vehicle.