1. A device for automatically setting an interlock between a plurality of robots, by editing a motion program of each robot, the device comprising: an interference area setting section for setting an interference area between the robots, using a simulation result based on the motion program of each robot; and a program editing section for inserting a motion command and a communication command before and after a command for moving each robot through the interference area of the motion program, the motion command being configured to direct the position and the orientation of each robot when the robot enters or leaves the interference area, and the communication command being configured to inform a robot of entering and leaving the interference area of the other robot, wherein the interference area setting section comprises a first interference area calculating part, the first interference area calculating part being configured to calculate two-dimensional coordinates of a moving path of a farthest point of each robot based on the simulation result, a two-dimensional interference area based on the two-dimensional coordinates of the moving path of each robot, and a first three-dimensional interference area formed by moving the two-dimensional interference area in the direction perpendicular to the two-dimensional interference area, and wherein the interference area setting section comprises a second interference area calculating part, the second interference area calculating part being configured to calculate a three-dimensional transit area of the moving path of each robot according to the motion program in the first three-dimensional interference area, by using a three-dimensional model of each robot, and a second three-dimensional interference area by checking interference between each three-dimensional transit area in the first three-dimensional interference area.