A mobile IP communication scheme in which the mobile computer can be operated using the mobile communication protocol such as Mobile IP even in the case where the home network is operated by the dynamic address allocation protocol such as DHCP is disclosed. The current location registration message to be transmitted by the mobile computer from the visited site to the mobile computer management device contains an information indicating that the dynamic address allocation has been received at the home network and an information capable of identifying the mobile computer, and the mobile computer management device carries out exchanges with the dynamic address management server on behalf of the mobile computer, so that the mobile computer which has received the dynamic address allocation at the home network can be operated at the visited site by using the mobile communication protocol.