The undulatory locomotion of nematode is investigated by the spatial-Fourier analysis of progressing body form. Motion pictures are taken digitally with a sampling frequency of 10 Hz over 10 sec. The dynamic features of behavior are visualized by plotting coefficients corresponding to the maximum power spectrum. The behavior of all nematodes is evaluated by a visual inspection every 2 sec, and divided into four “fundamental motions”; “travel”, “swing”, “mix”, and “rest”. Features of four motions are quantitatively calculated by applying the method in physiology. Firstly we calculated the areas of high and low frequency bands, H and L, respectively. Next the ratio H/Lwas averaged over every 2 sec. The averaged <H/L> ware corresponded to the four motions evaluated by observation in the same interval. <H/L> of the four motions are examined under food-rich and food-free conditions by the “F-test” at 5% significance. Those of four motions are significant between food-rich and food-free conditions.