Routers in a data transfer system relay data between the first node and each of the second nodes. A router includes a load value processing section and an aggregation decision section. The load value processing section obtains information about a load value of another router connected to a communications bus. The load value is a time delay caused by that another router and/or the throughput of that router. The aggregation decision section chooses one of the second nodes at which the data is to be received, and determines a transmission path between the second node chosen and the first node in accordance with information about the load value obtained from each router and information determined during a design process about the number of stages of routers from the first node through each second node and/or the length of data to be transferred.