To provide a passive active pitch flap mechanism for a windmill capable of making a flap motion tilting a blade to the downstream by air force acting in a windmill blade at excessive wind speed time simultaneously with a pitch motion changing a blade pitch angle, passively performing output control also actively performing a pitch angle change at extremely strong wind time of typhoon or the like.

This passive active pitch flap mechanism is characterized by providing a pitch actuator 9 for rotating a blade shaft in the blade shaft 2 of a windmill also holding the blade shaft 2 capable of swiveling by a flap shaft 4 and providing a spring 10 energizing the blade shaft to a normal position.