A wind-turbine control system is provided for each of a plurality of wind turbine generators constituting a wind farm, sends wind-turbine data about a controlled wind turbine generator to the wind-turbine control systems provided for the other wind turbine generators, and receives wind-turbine data about the other wind turbine generators from the wind-turbine control systems provided for the other wind turbine generators. Then, the wind-turbine control system controls the controlled wind turbine generator based on the wind-turbine data about the controlled wind turbine generator and the wind-turbine data about the other wind turbine generators. Therefore, the control of the wind turbine generators constituting the wind farm can be changed more swiftly according to the operational condition of the wind farm.