NOVELTY - The apparatus has a tower ventilation mechanism (40) that creates ventilation flow in an interior space of a tower (16). An interior space of a nacelle (12) and the interior space of the tower are isolated from each other so that air is prevented from flowing between nacelle and tower. The tower ventilation mechanism has an intake port (11a) and a discharge port (11b) that are placed on upper and lower portions of the tower. A fan (11c) forcedly creates the ventilation flow which flows downward in a vertical direction from the intake port to the discharge port.    USE - Renewable energy power generating apparatus such as Wind turbine power generating apparatus for generating electric power from renewable energy. Can also be used in tidal current power generating apparatus, ocean current power generating apparatus, and river current power generating apparatus.    ADVANTAGE - By providing a discharge port on a lower portion of the tower and carrying out forced ventilation by a fan, the air incorporated from the upper portion of the tower is uniformly distributed into the interior space of the tower. Thus, the effect of cooling the equipment is improved and appropriate and smooth ventilation of an interior space of a tower is carried out while preventing reverse flow. By providing a transformer chamber isolated from the ventilation space in the tower and cooling the transformer chamber by water cooling which has higher cooling performance than air cooling, the transformer used during normal operation of a renewable energy power generating apparatus is cooled effectively. By isolating the interior space of the nacelle and the interior space of the tower from each other, appropriate ventilation corresponding to each mechanism is carried out. Thus, the installation cost and power cost required for ventilation are reduced. The frequency of ventilation of filters for removing salt is reduced, and thus reduction of the ventilation cost is achieved. A stable combustion in the engine is achieved, and thus the backup generator is driven stably. By providing an impurity-substance removing section on intake port, the impurity substances are prevented from entering the interior space of the tower so as to protect the equipment installed in the interior space of the tower.    DESCRIPTION OF DRAWING(S) - The drawing shows a side view of a wind turbine power generating apparatus.    Wind turbine power generating apparatus (1)    Intake port (11a)    Discharge port (11b)    Fan (11c)    Nacelle (12)    Tower (16)    Tower ventilation mechanism (40)