We have built a multiple autonomous-robots simulator in order to study cooperative learning 'of multiagent systems. By using the simulator, experiments can be done for any tasks by any learning methods with some conditions. The simulator makes it possible to approach empirically to cooperative learning. 'Learning of multi- agent systems’ has not been founded yet as a field of study. Certain points have not been made clear: what is learning of multi-agent systems?; what questions should be raised?; what should be achieved; what should be considered as the cost (for example, should the cost of communication between agents be considered?). We intend to found a field, 'learning of multi-agent systems', through the experiment of a concrete example of appropriate complicatedness.