According to the present invention, a wind turbine generator system is provided which can not only remove the influence of salt damage in case the system is established off-shore, but even if the facility becomes larger, which can also cool equipment and the generator provided in the tower and can reduce the possibility of decreasing power generation efficiency. The wind turbine generator system of the present invention comprising a rotor having a hub and blades; a generator connected with the rotor by way of a main shaft connected with the hub; a nacelle which contains at least the generator and supports the rotor pivotally by way of the main shaft; a tower on a top of which the nacelle is supported, and opposite to the top the tower is fixed to a base, wherein a heat exchanger is provided at the tower close to the base and cooling medium passes through the heat exchanger by way of a pipe arrangement, and thereby the heat of the cooling medium and the heat of air inside the tower are exchanged and the air inside the tower is cooled.