This paper proposes a method of detecting waving hands from images as a key technology for man-machine interface. FFT is applied to time series of intensity images. The images are converted to low-resolution ones, and FFT is applied to each pixel of the low-resolution images. The proposed method is robust to lighting condition and individual difference of skin color, because it doesn't use color information at all. Experiments show the stability and robustness of the proposed method. Additionally, the method is applied to an omnidirectional vision images and an infrared camera, so as to show the wide applicability of the method.