1. A load decentralization method for decentralizing load centralized to a Mobility Anchor Point (MAP) of a hierarchical domain in a network where packets destined to mobile nodes in the network are transmitted to the mobile nodes via the MAP, the MAP including a table part including a plurality of elements for managing a corresponding relation of home addresses and Care-of-Addresses of the mobile nodes in the hierarchical domain, the method comprising the steps of: providing a same function as the MAP to at least a portion of routers situated in the hierarchical domain of the MAP; referring to one of the plural elements included in the table part; moving the one of the plural elements in the table part to the portion of the routers based on the number of times the one of the plural elements is referenced when a congestion of the MAP is detected; and actuating the portion of the routers to operate as a substitute of the MAP.