1. An apparatus for controlling a motion of a legged mobile robot having an articulated structure with at least a plurality of movable legs, comprising: an action-sequence generating unit which generates an action sequence by using motion units which store time-sequential motion of each joint; and a motion control unit which controls the motion of each joint in accordance with the action sequence generated; wherein each motion unit is constructed of basic dynamic attitudes and one or more moving attitudes, the basic dynamic attitudes including at least accelerations or angular accelerations of each joint at the end points of the motion unit, the end points corresponding to the start and the end of the motion, and the moving attitudes connecting the basic dynamic attitudes placed at the end points.