To generate power safely by securely braking rotation of a rotation shaft even when a hydraulic pressure is defective in a pinwheel of pitch control.

A power generator 10 for rotating a main shaft 8 by a wind received by a blade 5 and generating power by rotation force is provided. A pitch control function for changing a pitch of the blade 5 to the wind and controlling rotation of the main shaft 8 is provided. A brake device 12 for releasing brake by hydraulics pressure supply is provided on a rotation shaft 11 connected to the main shaft 8 through a step up gear 9. The brake device 12 is formed of a disc plate 13 provided on the rotation shaft 11 and a brake part 14 for pressing a brake pad by a spring 15 from front and back sides of the disc plate 13 and braking. A control part for determining that the rotation shaft 11 is braked on the basis of a detection signal from a brake detecting sensor for detecting that the rotation shaft 11 is braked, and controlling the pitch of the blade 5 to make a feathering state is provided.