A wind turbine able to generate power irrespective of a presence of and a state of a power grid is disclosed. Specifically, a wind power generation system is provided with a wind turbine, the wind turbine including a blade that rotates in response to the wind, a generator that rotates with rotation of the blade to generate power, and an auxiliary machine that controls a pitch angle of the blade. The auxiliary machine is driven by the generated power of a downwind type wind turbine to which a permanent magnet type generator is mounted and which generates power in a state in which a blade of the downwind type wind turbine rotating in response to the wind faces downwind.