A desired trajectory of a vertical component of a translation floor reaction force of a legged mobile robot 1, a vertical component of a total center-of-gravity acceleration or a body acceleration's vertical component of the robot 1 is determined, and a desired vertical position of a total center-of-gravity or body of the robot 1 is determined in such a manner that the vertical component of the translation floor reaction force, the vertical component of the total center-of-gravity acceleration or the body acceleration's vertical component agrees with the desired trajectory (that is, a dynamical equilibrium condition in the vertical direction is satisfied). Since the movement of the total center-of-gravity or the like in the vertical direction is determined after the desired trajectory of the vertical component of the translation floor reaction force or the like, a desired gait for the robot 1 suitable not only for walking but also for running can be generated.