In this paper, we propose a device for cooperation of multiple autonomous mobile robots. A device which enables local comnaunication, called Intelligent Data Carrier (IDC) is proposed. In this paper, we propose an algorithm to improve efficiency of iterative transportation tasks by autonomous mobile robots. An autonomous mobile robot gives name of its latest visited destination to an IDC which is located on a junction in a work area. An IDC summarize the information from robots and tell a direction which it expects best way to a destination which a robot want to go. By the proposed algorithm and system, mobile robots construct information of navigation and improve the efficiency of a task automatically. We verified the effectof the proposed algorithm by simulations and experiments.