To reduce a required buffer amount and to reduce the scale of whole equipment when processing for sharing the same transmission band is performed by plural types of communication data.

Transmission format judging parts 201 to 203 corresponding to a plurality of data generation parts 101 to 103 by one to one judge transmission formats that the individual data generation parts 101 to 103 can use from the priority of communication data in the data generation parts 101 to 103 that the priority management section 107 manages and the individual data amounts of the data generation pats 101 to 103, judge the transmission bands that the individual data generation parts 101 to 103 can use by mutually giving information of the transmission formats in the data generation parts 101 to 103 and transmit communication data corresponding to the judged transmission formats through a transmission line interface part 105 to the transmission line.