In a wireless network in which an addressing server allocates an IP address, there are provided an IP address acquisition method, a communication apparatus and a roaming method whereby a terminal can automatically acquire an IP address from the addressing server. An IP address acquisition method for acquiring an IP address for a terminal 14 from a addressing server 18 comprises the steps of: providing the terminal 14 with a temporary IP address in a case that a first communication apparatus 10 is not capable of connecting with a second communication apparatus 12 when the first communication apparatus 10 receives an IP address request message from the terminal 14; discarding the temporary IP address from the terminal 14 when it becomes possible to connect with the second communication apparatus 12 and a communication path is established; and acquiring an IP address for the terminal 14 from the addressing server 18 via the communication path.