PURPOSE: To reduce the torque itself generated by a windmill and improve safety by detecting a wind velocity exceeding a dangerous wind velocity point and operating a pitch control unit from outside by means of this signal.

CONSTITUTION: Multiple blades 1 are fitted around a hub 2 and generate the rotating torque by means of a wind velocity (a) to rotate the hub 2 in the rotating direction (b). This rotation is transmitted to a main shaft 3 and is fed to a load machine. When the wind velocity (a) is strong, a feed nut 12 is rotated, and a feed screw 10 supported by a support 11 is advanced to move a slider 5 through a roller 9 and a rod 8. A pitch control unit constituted with a slider 5, a weight 6, and a spring 7 is changed to an angle corresponding to the wind velocity (a) of the blades 1.