The present invention provides a floating offshore wind turbine capable of suppressing yawing of a nacelle caused by a gyro effect which is a cause of adverse influence of power generating efficiency of a wind turbine and endurance of devices thereof. The floating offshore wind turbine 10 includes a rotor 11 which is rotated by wind, a nacelle 13 in which a rotation shaft 12 of the rotor 11 is accommodated, and a tower 15 including a turning seated bearing 14 which supports the nacelle 13 such that the nacelle 13 can turn with respect to a sea surface P to exert a weathercock effect. The tower is provided with yawing suppressing means 16 which suppresses yawing T of the nacelle 13. According to this, it is possible to suppress the yawing T of the nacelle 13 generated by a gyro effect caused by yawing Ω generated in the floating body 31 by waves of the sea surface P.