An object of the present invention is to avoid the situation where data to be transmitted have to be discarded, even when a network to which the data is to be transmitted is unavailable. The electronic control unit has: a determination part that executes a first determination process for determining whether a network to which data is to be transmitted is available or not; and a transmission part that executes a first transmission process for transmitting the data to the network when it is determined that the network is available, and executes a storage process for storing the data in a storage medium when it is determined that the network is unavailable. The electronic control unit executes the same processes for another network as well.