It is determined whether the motion state of legs 2, 2 is a one-leg supporting state or a two-leg supporting state, and a total floor reaction force is estimated based on a motion equation of the center of gravity of a bipedal movable body 1. If the motion state of legs 2, 2 is the one-leg supporting state, the estimated value of the total floor reaction force is used as an estimated value of the floor reaction force on the leg 2 which is landed. When the motion state changes to the two-leg supporting state, a vertical component of the floor reaction force on the rear leg is estimated from the MP height of the front leg based on a predetermined correlation between the MP height of the front leg and the vertical component of the floor reaction force on the leg.