A computer 11 of a ship monitoring device 1 arranges one kind of transmission data between two consecutive start control codes and two consecutive termination control codes. The computer 11 also arranges information indicating a type of the transmission data between the transmission data and the start control codes and between the termination control codes and the transmission data. In this way, the transmission data is transmitted in form of packet data. Therefore, transmission data in information communication between ships and sensed information in information communication of fenders can be easily distinguished from each other. In addition, a type of information transmitted as the transmission data can be easily identified.
