A wind
turbine generator, an active damping method thereof, and a
windmill tower in which vibrations of the wind
turbine generator itself or the
windmill tower can be reduced at low cost are provided. The acceleration due to vibrations of a
nacelle (13) is detected with an
accelerometer (17) attached to the
nacelle (13). In an active damping unit (20), a
pitch angle of
windmill blades (12) for generating a thrust on the windmill blades (12) so as to cancel out the vibrations of the
nacelle (13) is calculated on the basis of the acceleration, and the
pitch angle is output as a blade-
pitch-angle command δθ* for damping. On the other hand, in a pitch-angle
control unit (30), a
pitch angle of the windmill blades (12) for controlling the output to be a predetermined value is calculated, and the
pitch angle is output as a blade-pitch-angle command θ* for output control. The blade-pitch-angle command δθ* for damping is combined with the blade-pitch-angle command θ* for output control using a subtracter (40). The
pitch angle of the windmill blades is controlled on the basis of the resulting blade-pitch-angle command after combining.