PURPOSE: To restrain wasteful energy consumption to the possible minimum level in a braking energy regenerative device.

CONSTITUTION: In a braking energy regenerative device to basically open a working fluid storage means 30 in the atmosphere at engine stopping time by converting fluid pressure energy into braking energy by actuating an energy converting means 40, which is interposed in fluid passages P1 and P2 between the working fluid storage means 30 and a pressure accumulating means 20 and is connected through a connecting-disconnecting means 51, by a pump at braking time, and on the other hand, utilizing it as departing-accelerating energy by actuating the means by a motor at departing-accelerating time, the device is provided with an engine stall detecting means to detect this when an engine is switched to a stopping condition from an actuating condition, and is constituted so that the working fluid storage means 30 is not opened in the atmosphere in a prescribed time when the fact that the engine is switched to a stopping condition from an actuating condition is detected by the engine stall detecting means.