An operation instruction list including starting points and ending points of trajectories of a plurality of robot arms is generated (a trajectory definition data generation process). Order of generation of trajectories is determined in accordance with the operation instruction list (a generation order determination process). A trajectory of a specific robot arm included in the operation instruction list is generated in accordance with a starting point and an ending point such that the trajectory avoids obstacle spaces registered in the obstacle memory when trajectories of other robot arms are generated (a trajectory generation process). A sweeping space in which a structure of the arm sweeps when the robot arm is operated along the generated trajectory is added to the obstacle memory as an obstacle space to be avoided by the other robot arm (an obstacle registration process).