To transfer data to a remote place by data communication between a plural number of movable robots even by a weak electric wave.

A wireless device to give a command and a plural number of the movable robots to receive a wireless data are arranged in a working space. Each of the movable robots receives the wireless data of the same frequency band and stores the data in a memory of a main body. The movable robot transmits the stored received data when it meets with another robot not receiving the data at a place where it moves. The data is moved to a place difficult to transmit from the wireless device by repeatedly transferring the data between the movable robots like the above.