To provide a windmill for wind-power generation capable of further increasing rotation efficiency.

The windmill 1 is formed by arranging fixed blades 3 in the periphery of the cross-flow type rotary blades 2. The rotary blades 2, as a whole, are arranged to expand and open upward while being twisted. When wind blows against the rotary blades 2 to start rotation, force acts in a direction to float the rotary blades 2 from the support of a fixed shaft 5. Thus, friction on the support is reduced and reduction of torque is eliminated by that portion, and thereby, rotation efficiency is increased.