The present invention, in each hierarchy domain, and manages association between care-of-address of the mobile body varies by moving a valid address in the hierarchy domain of the mobile object does not change due to the movement of the hierarchy domain table means of the mobile base node and, in a network where packets of all mobile destined reaches the mobile via the mobile base node, a load distribution method for distributing the load of the mobile base node, at least a portion of the router in the hierarchy domain motion composed of base functions provided router provided with the base node same functions as, when it detects congestion of the mobile base node moving some elements of the table means to the base functions provided router, move starting from a root function includes a router by operating as a node, move the other routers in the hierarchy domain when the mobile base node has fallen into the congestion It is possible to perform load balancing by activating as a point node.