To design the artificial feet for the amputees, the behaviors of human feet and of the conventional artificial feet in locomotion are observed using a high-speed cine-camera of 400 frames per second. Angular displacement of each joint of lower limb is analyzed with synchronized data of floor reactions. Some remarkable differences between the behavior of human feet and of artificial feet are recognized in the phase of heel contact and push off. These differences can not be find from the data of conventional clinical gait analysis using normal speed cine-camera of 10-60 frames per second. Besides above, it is recognized that high speed cinematograph will give us more information on the contraction of muscles than E.M.G. method.