A distribution route construction method includes: transmitting, in a data distribution system, at least one check packet to a plurality of terminals within a network from a check packet transmission terminal; checking a reply packet from the plurality of terminals; grouping the plurality of terminals into a first terminal group including a first terminal whose reply packet reaches the check packet transmission terminal and a second terminal group including a second terminal whose reply packet does not reach the check packet transmission terminal; changing a designation terminal for data communication to reduce communication data traffic between the first terminal group and the second terminal group; and reconstructing distribution routes based on the checking and the changing.