1. A system for controlling motion of a mobile robot such that the robot moves to a desired position, comprising: a. means provided to be manipulated by an operator for inputting at least one of the desired position and orientation of the robot at a time when the robot reaches the desired position; b. means for displaying an image indicative of the inputted desired position and orientation on a display; c. means for controlling the motion of the robot based on the inputted desired position and orientation; d. means for setting an upper limit of a distance from a current position of the robot to the desired position; and e. means for invalidating the inputted desired position when the distance exceeds the upper limit; and the means for displaying displays a first image indicative of the inputted desired position and orientation by numeric values or language including at least the numeric values and a second image indicative of the inputted desired position and orientation by graphics composed of arrows whose directions and lengths are changeable.