PURPOSE: A brake system is provided to reduce vibration and noise caused by a yaw brake disk by reducing the weight of the yaw brake disk and forming an opening in the yaw brake disk. CONSTITUTION: A brake system(400) comprises a yaw brake disk(410) and a braking unit(420). The yaw brake disk is formed along the upper surface of a tower(100). One side of the braking unit is installed in a lower part of a nacelle so that the braking unit rotates with the nacelle. The other side of the braking unit implements braking by pressing one side of the yaw brake disk. In the yaw brake disk, an opening is formed to reduce the area of the yaw brake disk. The opening is located inside or outside a pressing section in the radial direction of the yaw brake disk not to overlap the pressing section of the braking unit.
