To provide a power regenerating device for a vehicle in which a rotary electric machine continues to operate as a generator until the rotational speed of the rotary electric machine is reduced to a prescribed rotational speed even if a brake effect when starting regeneration of power causes reduction in the rotational speed of the rotary electric machine.

The power regenerating device 1 for a vehicle comprises a fan 10 that is rotative by traveling wind received during the traveling of the vehicle, the rotary electric machine 20, a power regenerating circuit 30, a battery 40, and a rotational speed detector 50 that detects the rotational speed of the rotary electric machine 20. In the power regenerating device 1 for a vehicle, the power regenerating circuit 30 starts power regeneration when the rotational speed of the rotary electric machine 20 becomes not lower than the prescribed rotational speed, and terminates the power regeneration at a speed lower than the rotational speed of the rotary electric machine 20 at the start of the power regeneration.