In a wireless packet transmission system that includes multiple wireless basestations and one or more wireless terminals belonging to one of the wireless basestations, transmission trees extending from two or more wireless basestations as root stations are used. Each of the wireless basestations has a tree table configured to record the root stations in association with the ID information about the transmission trees. When receiving a packet, each of the wireless basestations determines the transmission tree to be used for the packet transmission, and transmits the packet to a next node along the determined transmission tree.