A wind turbine generator having a large opening area for air intake and exhaust while maintaining tower strength and having a sufficient cooling performance is provided. In the wind turbine generator, a rotor head rotating when receiving wind power with wind turbine blades drives a generating machine provide inside a nacelle to generate electric power. The nacelle is provided on an upper end portion of a tower (2) standing upright on a foundation. Outer air is introduced into the tower from a tower opening. (20) provided on a surface of the tower (2) to cool an inner space of the tower. The wind turbine generator includes a recessed cylindrical portion (21) extending from the tower opening (20) toward the inner side of the tower. Air can pass through pressure loss elements provided on a part or all of a surface making up the cylindrical portion (21), and an effective opening area where the pressure loss elements are provided is larger than an actual opening area of the tower opening (20).
