In one embodiment, a wind-power generating system 10 includes: a lightning protecting device including a receptor 70 provided on a blade surface and a lightning conductor 73 grounding the receptor 70; an airflow generating device 60 provided on the blade surface and including first and second electrodes 61, 62 separated via a dielectric 63; a discharge power source 65 including switches 90, 91 able to connect the first and second electrodes 61, 62 to output terminals 84, 85 respectively and a switch 92 able to connect the first or second electrode 61, 62 to a grounding conductor 100; and a thundercloud detecting device detecting information regarding thundercloud approach. When the information regarding the thundercloud approach is detected, the second electrode 62 is connected to the grounding conductor 100 and the first and second electrodes 61, 62 are disconnected from the output terminals 84, 85.