In the case where a single user selectively uses plural wireless communication terminals by mounting and demounting a subscriber identification card thereon and therefrom, user convenience in such selective use of the plural terminals can be enhanced by synchronizing user data among those plural terminals. For this purpose, at least updated portion of the data stored in the memory in terminal is uploaded from the first terminal 10a on which SIM card (subscriber information card) 12 is mounted, to a server 50 via a communication network 20, according to a user's request or automatically. After the SIM card 12 demounted from the first terminal is mounted on the second terminal 10b or 10c, data to be downloaded to the second terminal from the server 50 is determined according to the user's request or automatically, and the data is downloaded to the second terminal from the server 50. In the second terminal, thus downloaded data is used to update the contents in the memory.