A mobile packet communication system has a plurality of mobile terminals movable between a plurality of auxiliary networks. Each of the mobile terminals has an inherent address processing layer for adding a packet header based on the inherent address thereof to transmission data from a higher layer, and a positional address processing layer for adding a packet header based on the positional address thereof to the transmission data to which the packet header based on the inherent address has been added by the inherent address processing layer. The packet headers contain no header information representing an association between the inherent address and the positional address. The mobile packet communication system facilitates a control process for maintaining data relative to an association between addresses and reduces an amount of communications required by such a control process.