To realize data communication by a data terminal connecting directly to the communication terminal.

A speech section 13 connects to a radio communication network 2 by a radio communication section 12 by means of a radio channel to realize a voice speech via the radio communication section 12. Furthermore, a signal conversion section 15 conducts protocol processing and data modulation- demodulation or the like so as to allow an external data terminal 3 not corresponding to the radio communication network 2 to make communication via the radio communication network 2. A connection state recognition section 16 monitors whether or not the external data terminal 3 connects to an external device interface section 14. Then a communication mode selection means 18a of a control section 18 sets the communication mode so that a voice speech with an activated speech section 13 is conducted when the connection state recognition section 16 detects non-connection of the external data terminal 3 and so that data communication by the external data terminal 3 with the activated signal conversion section 15 is conducted when the connection state recognition section 16 detects connection of the external data terminal 3, respectively.