To implement a dynamic, elegant motion performance of an actual robot, a motion editing system is provided which includes a motion editor to edit motions of an upper body and whole body of the robot and a foot trajectory editor to create a gait pattern and lower-body motion to stabilize the entire robot. The foot trajectory editor includes the same gait pattern generator and motion stabilized as those installed in the actual robot. Before performing the edited motions on the actual robot, the motions are created, corrected and stabilized on a 3D viewer.