PROBLEM TO BE SOLVED: To provide a vertical axis wind turbine having an overspeed prevention structure including a quite simple structure without using any surplus control parts so as to restrict only an axial motion of a blade shaft supporting a blade and a self-rotation of the blade shaft and enabling its manufacturing to be attained in less-expensive manner.SOLUTION: In this invention, one end part of a blade shaft 21 is held at a rotary hub and a blade is fixed to the other end of the blade shaft 21. This blade shaft 21 can be moved in a radial direction due to a centrifugal force accompanied by rotation of the blade and at the same time the blade shaft is twisted around an axis of its radiation direction to cause a wind receiving area of the blade and an effective pitch angle of the blade to be changed and there is provided a restricting structure for restricting a motion of the blade shaft in its radial direction and its self-rotation.SELECTED DRAWING: Figure 1
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