To provide a wind power generation device capable of effectively using both of horizontal air stream and vertical air stream and efficiently generating power.

This windmill for wind power generation comprises a central shaft 11; a first vane 12 provided around the central shaft so that a wind receiving surface may be inclined to an axial direction of the central shaft 11 and rotating with the central shaft 11; and a second vane 13 provided outside the first vane 12 so that the wind receiving surface may become parallel to the axial direction of the central shaft 11 and rotating with the first vane 12. The second vane 13 is positioned on a base end side, and constituted so as to be inclined with a shaft 16 parallel to the central shaft 11 centered.