The invention provides a wind turbine generating apparatus capable of controlling a temperature in a rotor head. In a wind turbine generating apparatus in which a driving/generating mechanism coupled to a rotor head having wind turbine blades attached thereto is housed in a nacelle, and control devices are housed in a hub of the rotor head, an air circulation guide is provided for allowing air to circulate between an inside of the rotor head and an inside of the nacelle via a communication path formed between the rotor head and the nacelle.