To grasp a position of a floor reaction working point related to a bipedal walk moving body such as man in a relatively simple manner in real time without using a plurality of types of correlation data.

During movement of the bipedal walk moving body such as walking on a flat land, a position of the centroid G0 of the bipedal walk moving body, a position of an ankle joint 12 of each leg 2 and a position of a metatarsophalangeal joint 13a of a foot flat part 13 are grasped one by one, and a horizontal position of the floor reaction working point of the grounded leg 2 is estimated according to their relative positional relationship. When the centroid G0 is on the rear side of the ankle joint 12 in the running direction of the bipedal walk moving body, a horizontal position of the ankle joint 12 is set to be the horizontal position of the floor reaction working point. When the centroid G0 is between the ankle joint 12 and the metatarsophalangeal joint 13a, a horizontal position of the centroid G0 is set to be the horizontal position of the floor reaction working point. When the centroid G0 is on the front side of the metatarsophalangeal joint 13a, a horizontal position of the metatarsophalangeal joint 13a is set to be the horizontal position of the floor reaction working point. A vertical position of the floor reaction working point is estimated on the basis of the distance in the vertical direction from the ankle joint 12 to a grounded surface.