A mobile terminal comprising: a main home agent selecting section for selecting a main home agent apparatus (50-1, 50-4, 50-5) to carry out location management of the mobile terminal, the mobile terminal communicating with an access point apparatus located in a subnet configuring a domain network, and the mobile terminal moving between subnets in a same domain network or between domain networks which are different in service form, wherein the mobile terminal further comprises, a network layer communication processing section for acquiring a home prefix information from a router located in the subnet of a moved-in domain network and determining whether the moving of the mobile terminal is the moving between the subnets in the same domain network or the moving between the domain networks which are different in service form, a mobile IP processing section for registering an 2 nd home address (HoA-2) and a 2 nd care of address which are effective as a home address and a care of address in the moved-in domain network and acquired by the mobile terminal, to a 2 nd home agent apparatus managing the moved-in domain network, and registering an 1 st home address (HoA-1), which is effective as a home address in a moved-out domain network and acquired by the mobile terminal, and the 2 nd home address (HoA-2) as a care of address to a 1 st home agent apparatus managing the moved-out domain network, when the network layer communication processing section determines the moving of the mobile terminal is the moving between the domain networks which are different in service form, and a home agent registering section for registering a main home address (HoA-M) as a home address and the 2 nd home address as a care of address, of the mobile terminal in a home domain network, to the main home agent apparatus managing the home domain network, and wherein the main home agent selecting section further is for measuring a time or times of stays in each domain network, whereby when at a certain time a stay time reaches a predetermined time, the domain network belonged at that certain time is taken as a home domain network. a main home agent selecting section for selecting a main home agent apparatus (50-1, 50-4, 50-5) to carry out location management of the mobile terminal, the mobile terminal communicating with an access point apparatus located in a subnet configuring a domain network, and the mobile terminal moving between subnets in a same domain network or between domain networks which are different in service form, wherein the mobile terminal further comprises, a network layer communication processing section for acquiring a home prefix information from a router located in the subnet of a moved-in domain network and determining whether the moving of the mobile terminal is the moving between the subnets in the same domain network or the moving between the domain networks which are different in service form, a mobile IP processing section for registering an 2 nd home address (HoA-2) and a 2 nd care of address which are effective as a home address and a care of address in the moved-in domain network and acquired by the mobile terminal, to a 2 nd home agent apparatus managing the moved-in domain network, and registering an 1 st home address (HoA-1), which is effective as a home address in a moved-out domain network and acquired by the mobile terminal, and the 2 nd home address (HoA-2) as a care of address to a 1 st home agent apparatus managing the moved-out domain network, when the network layer communication processing section determines the moving of the mobile terminal is the moving between the domain networks which are different in service form, and a home agent registering section for registering a main home address (HoA-M) as a home address and the 2 nd home address as a care of address, of the mobile terminal in a home domain network, to the main home agent apparatus managing the home domain network, and wherein the main home agent selecting section further is for measuring a time or times of stays in each domain network, whereby when at a certain time a stay time reaches a predetermined time, the domain network belonged at that certain time is taken as a home domain network. registering an 2 nd home address (HoA-2) and a 2 nd care of address which are effective as a home address and a care of address in the moved-in domain network and acquired by the mobile terminal, to a 2 nd home agent apparatus managing the moved-in domain network, and registering an 1 st home address (HoA-1), which is effective as a home address in a moved-out domain network and acquired by the mobile terminal, and the 2 nd home address (HoA-2) as a care of address to a 1 st home agent apparatus managing the moved-out domain network,