To secure sufficient stability in a single-leg supporting state by retaining a favorable grounding state between the sole of the foot part and a ground plane in a walking operation and smoothly perform the walking operation of this type of legged robot.

This foot part structure is so constituted that a movable body capable of grasping the ground plane is provided in the sole of the foot part, when the foot sole grounds the ground plane in the walking operation, the movable body grasps the ground plane to retain the favorable grounding state between the foot sole and the ground plane.