PURPOSE: To prevent the hydraulic pump-motor of a braking energy regeneration device from rotating reversely at the time of stopping a vehicle.

CONSTITUTION: This device is provided with a hydraulic oil tank 10 and an accumulator 11 mounted on a vehicle body, a hydraulic pump-motor 12 connected to the driving shaft 26 of the vehicle body, an oil passage for connecting the hydraulic oil tank 10 to the hydraulic pump-motor 12, and oil passages 16, 17 for connecting the hydraulic pump-motor 12 to the accumulator 11. This device is also provided with an oil passage 37 for connecting the oil passage 16 to the hydraulic oil tank 10, and an electromagnetic switching valve 40 for releasing oil pressure in the oil passage 16 to the hydraulic oil tank 10 through the oil passage at the time of valve opening.