When generating a gait for a legged mobile robot 1 which has floating periods in which all the legs 2 of the robot float in the air and landing periods in which any of the legs 2 is in contact with the floor appearing alternately, a desired ZMP is set at any point in time in the floating periods and the landing periods, and a desired gait is generated in such a manner that the horizontal component of the moment produced about the desired ZMP by the resultant force of gravity and an inertial force caused by a movement of the robot with the desired gait is 0. The desired ZMP is set to be substantially continuous for all the periods in the gait. Furthermore, as a dynamics model for determining the desired gait, an approximate model is used which is arranged so that the moment, about a certain point of application, of the resultant force of the inertial force and gravity calculated using the model depends on the position of the point of application.