Vertical-axis wind turbine composed of first and second independent coaxial rotors (1 and 2), which coincide in the horizontal position, when mounted on one and the same vertical shaft (35), with the ability to rotate in opposite directions. The first and second rotors (1 and 2) bear blades (10 to 13) and (20 to 23) which are articulated to said rotors on non-coinciding vertical shafts (16-26). The blades (10 to 13) and (20 to 23) have curved active surfaces directed, on each rotor, in the same direction but in the opposite direction from the blades of the other rotor.