A high-speed forward dynamics computation for a link system wherein links are connected via joints, has: (1) first step for adding a joint one by one in series between the links to an initial link condition wherein all of the respective links are not connected via the joints so as to obtain a force of constraint acting at the joint between the links at that time; (2) second step for removing the joint in a reverse order as that of the first step so as to compute a final force of constraint at respective joints; (3) third step for computing an acceleration of respective links by utilizing applied forces obtained in the first step and the second step; and (4) fourth step for computing a joint acceleration by utilizing the accelerations of the links positioned at both ends of respective joints obtained at the third step.