To solve difficulties in an increase in efficiency of wind power generation, since the wind mill of the existing vertical axis wind power generator has mainly a simple blade cross sectional shape, positive countermeasures against wind, attentive countermeasures according to nature of wind, or the like cannot be taken.

In this vertical axis wind power generator, blades 1, 2 are arranged at both the ends of main arms 5, 6 orthogonal to a rotary shaft, the directions of both the blades are attached in the same direction, a blade 1 receiving wind from a tip obtains larger lift by a flap plate to improve rotational force and also increase the number of revolutions, and a blade 2 receiving wind from a rear end can efficiently convert wind pressure into rotational force by the flap plate. Thereby, in a specific wind speed area and at the time of a breeze, it can lead to improvement and betterment in power generation, and securance of rotational force in starting.