In multi-robot system, cooperation is needed to execute tasks efficiently. The purpose of this study is to realize cooperation among multiple robots using interactive communication. An important role of communication in multi-robot system is to make it possible to control other robots by intention transmission. We consider that multi-robot system can be more and more adaptive by treating communication as action. In this report, we adopt action adjustment function to achieve cooperation between robots. We also run some computer simulations of collision avoidance as an example of cooperative task, and discuss the results. Keywords. Q-learning, Multi-Robot System, Communication, Cooperation, Mobile Robot