PURPOSE: To permit stable operation of a wind mill which is always directed to the wind, by controlling and adjusting the deflection phenomenon of being inclined with respect to the wind direction which is generated by the reaction generated through bevel-gear transmission, by a steering vane.

CONSTITUTION: When the power supplied from a propeller wind mill 3 is applied onto a generator 12 through a bevel gear, the loading torque increases, and the reaction of the gear torque acts as turning force onto a swivel revolution board 2, and the wind mill 3 tends to operate, titled with respect to the direction of the wind. The loading torque is transmitted to a deflection steering vane 9 through a differential shaft 7 and a gear 8, and acts in the direction for turning- back the propeller wind mill 3. The wind mill 3 is further deflected and increases the retaining force, receiving the reaction of the wind, and thus the wind mill is operated stably, always oppositely directed to the wind direction.