A desired gait is generated so as to satisfy a dynamical equilibrium condition concerning the resultant force of gravity and an inertial force applied to a legged mobile robot 1 using a dynamics model which describes a relationship among at least a horizontal translation movement of a body 24 of the robot 1, a posture varying movement in which the posture of a predetermined part, such as the body 24, of the robot 1 is varied while keeping the center of gravity of the robot 1 substantially unchanged and floor reaction forces generated due to the movements and is defined on the assumption that a total floor reaction force generated due to a combined movement of the movements is represented as a linear coupling of the floor reaction forces associated with the movements. The dynamics model represents movements as a movement of a body material particle or the like and a rotational movement of a flywheel. The desired gait adapted for not only walking but also running or the like can be generated with a reduced amount of calculation.