A wind power generating device includes: a fan blade; a rotating device, which is kinetically connected to the fan blade so as to rotate with the fan blade; a securing ring being configured to surround the rotating device; and a power generating device with a power input shaft kinetically connected to the rotating device. By a kinetic assisting device formed by the rotating device and the securing ring, the wind power generating device is capable of maintaining a time period of electricity generation even when wind speed is low or none due to vehicle stop, and further enhances the practical requirement of wind power generating device as being installed in a vehicle.