[Problem] To reduce damage to a windmill blade due to a separation phenomenon occurring at the back surface of the windmill blade. [Solution] A wind power generation device wherein a rotor having lift-type windmill blades receives wind and rotates, thereby driving a generator and generating power, said wind power generation device characterized in that apertures, which connect the outside of the windmill blade and a closed space in the interior of the blade and can be opened/closed, are provided on the blade rear surface of the windmill blades.
