At the present invention, a pitch controller (111), uninterruptible power supply (112), and rotational speed detector (114) are disposed in the rotor (1) in a wind turbine. When a slip ring failure or wire breakage occurs, the pitch controller (111) internally creates a pitch angle command so as to control the pitch angle.
Accordingly, even if the slip ring (7) between the rotor (1) and nacelle (2) fails in the wind turbine, pitch angle control is performed reliably.