When a terminal moves from a serving cell to a target cell, the carrier in use is switched to the primary carrier of the serving cell and then handed over to the target cell. Hereupon, handover is performed by switching the carrier used by the terminal operating with the primary carrier of the serving cell to the primary carrier of the target cell to perform handover. When the terminal has fully entered the target cell, the best carrier is selected from among the carriers available to the target cell, thus allowing the terminal to perform frequency conversion to the best carrier.