With a simple and low-cost structure, it is possible to introduce a sufficient amount of external wind while suppressing power consumption, and thereby, inside a nacelle and a tower are satisfactorily cooled. A wind turbine generator, in which a rotor head generates power by driving a generator installed inside a nacelle and in which the nacelle is installed at a top end of a tower, wherein an introducing vent that takes the external wind into an internal space in the wind turbine generator is provided at a portion of an outer circumference surface of the tower or the nacelle that receives positive pressure due to the external wind; and an exhaust vent that externally exhausts cooling air in the internal space is provided at a portion of an outer circumference surface of the tower or the nacelle that receives the negative pressure due to the external wind.