A horizontal axis wind turbine apparatus comprising: - a main turbine unit supporting a horizontal axis turbine rotatably around a horizontal axis, wherein the horizontal axis turbine has a plurality of blades (B1, B2, B3) and is adapted to rotate around the horizontal axis by receiving wind; - a tower supporting the main turbine unit pivotably in the horizontal direction, and allowing the main turbine unit to pivot in accordance with a direction of wind received by the blades (B1, B2, B3); - a pivoting position detector provided either on the main turbine unit side or on the tower side, for detecting a position (Ψ) of the main turbine unit in its pivoting direction; - a blade rotation angle detector provided on the main turbine unit, for detecting a rotation angle (Φ) of each of the blades (B1, B2, B3) in the rotational direction of the horizontal axis turbine; - a blade pitch angle changing mechanism provided on the main turbine unit, for changing a pitch angle of each of the blades (B1, B2, B3) independently in a direction that increases the pitch angle or in a direction that decreases the pitch angle; and - a pitch angle controller for controlling the blade pitch angle changing mechanism so as to continuously adjust the pitch angle of each blade (B1, B2, B3) according to the rotation angle (Φ) of each blade while the horizontal axis turbine is rotating, characterized in that - the pitch angle controller is adapted to acquire said position (Ψ) and the rotation angle (Φ) from the pivoting position detector and the blade rotation angle detector respectively, to calculate a rate of change (ΨD) of said position (Ψ), to perform control so that a torque generated by the horizontal axis turbine acts in the direction opposite to the direction of a change of the position (Ψ) of the main turbine unit by setting the pitch angle to the fine side for blades that move to the upwind side according to a change direction of the position (Ψ) of the main turbine unit and by setting the pitch angle to the feather side for blades that move toward the downwind side according to a change direction of the position (Ψ) of the main turbine unit, and to calculate an amount of change of the pitch angles of each of the blades (B1, B2, B3) according to the increase in the rate of change (ΨD) of the position (Ψ), wherein the calculated values increase in accordance with the increase in the rate of change (ΨD) of the position (Ψ). - a main turbine unit supporting a horizontal axis turbine rotatably around a horizontal axis, wherein the horizontal axis turbine has a plurality of blades (B1, B2, B3) and is adapted to rotate around the horizontal axis by receiving wind; - a tower supporting the main turbine unit pivotably in the horizontal direction, and allowing the main turbine unit to pivot in accordance with a direction of wind received by the blades (B1, B2, B3); - a pivoting position detector provided either on the main turbine unit side or on the tower side, for detecting a position (Ψ) of the main turbine unit in its pivoting direction; - a blade rotation angle detector provided on the main turbine unit, for detecting a rotation angle (Φ) of each of the blades (B1, B2, B3) in the rotational direction of the horizontal axis turbine; - a blade pitch angle changing mechanism provided on the main turbine unit, for changing a pitch angle of each of the blades (B1, B2, B3) independently in a direction that increases the pitch angle or in a direction that decreases the pitch angle; and - a pitch angle controller for controlling the blade pitch angle changing mechanism so as to continuously adjust the pitch angle of each blade (B1, B2, B3) according to the rotation angle (Φ) of each blade while the horizontal axis turbine is rotating, - the pitch angle controller is adapted to acquire said position (Ψ) and the rotation angle (Φ) from the pivoting position detector and the blade rotation angle detector respectively, to calculate a rate of change (ΨD) of said position (Ψ), to perform control so that a torque generated by the horizontal axis turbine acts in the direction opposite to the direction of a change of the position (Ψ) of the main turbine unit by setting the pitch angle to the fine side for blades that move to the upwind side according to a change direction of the position (Ψ) of the main turbine unit and by setting the pitch angle to the feather side for blades that move toward the downwind side according to a change direction of the position (Ψ) of the main turbine unit, and to calculate an amount of change of the pitch angles of each of the blades (B1, B2, B3) according to the increase in the rate of change (ΨD) of the position (Ψ), wherein the calculated values increase in accordance with the increase in the rate of change (ΨD) of the position (Ψ).