The invention provides an address information setting method such that when home agent information such as an address of a home agent, which is basic information for activating mobile IP protocol processing, is acquired, it is made possible to perform communication that satisfies requirements desired by a user or an application by starting mobile IP protocol processing using home agent information acquired according to an instruction of a user. In addition, it is possible to reduce the work burden on a user for making settings and provide a mobile terminal with high convenience by automatically acquiring home agent information on a link at a time specified by the user.