Mobile IPv6 assigns MN (Mobile Node) with a fixed home address in order to guarantee an arrival to MN 7. A SIP process of HA (Home Agent) 2 is provided with a unit for notifying Binding information of MN to a presence server 1. Alternatively, the presence server 1 is provided with a unit for requesting HA 2 for the Binding information of MN. An information delivery server 3 is provided with a unit for acquiring a Care of Address of MN from the presence server 1 and selecting information corresponding to the Care of Address. Presence service can be provided to MN existing in a network other than a home network.