An RSSI detecting unit measures a receiving power level of a signal receive from a base station, and notifies a mode change control unit of the measurement result. A Ec/Io detecting unit measures a Ec/Io level of the signal received from the base station, and notifies the mode change control unit of the measurement result. The mode change control unit discriminates the change of the operation mode in consideration of not only the receiving power level, but also the Ec/Io level, and does not change the Simultaneous-Mode from the Hybrid-Mode unless at least the Ec/Io level exceeds a threshold line.