Automatic operation system, automatic operation control method, data ecu, and automatic operation ecu

The present invention addresses the problem of flexibly reducing the data transmitted from an ECU to another ECU depending on the circumstances. In this automatic operation system, an automatic operation ECU and a plurality of data ECUs are connected via a first network. The automatic operation ECU is equipped with: a first communication unit that sends and receives automatic operation data to and from the plurality of data ECUs; and a vehicle control unit that controls a vehicle on the basis of the automatic operation data transmitted from the plurality of data ECUs. Each of the data ECUs is equipped with: a data constructing unit that constructs the automatic operation data to be transmitted to the automatic operation ECU; and a second communication unit that sends and receives automatic operation data to and from the automatic operation ECU. If a predetermined event occurs, the data constructing unit of the data ECU, in which the predetermined event has occurred, among the plurality of data ECUs is configured so as to construct automatic operation data so that the total amount of the automatic operation data, transmitted by the data ECU in which the predetermined event has occurred, does not exceed a predetermined amount of data.