To provide an external input/output device for a mobile phone that can be connected to a mobile phone wirelessly and access the mobile phone for data transmission reception even when the mobile phone is busy with a speech.

The mobile phone 1 includes an information storage section 18 to store data and a wireless communication section 21 for transmitting/ receiving data to/from the external input output device 3. The external input output device 3 includes a wireless communication section 32 for wirelessly transceiving data to the wireless communication section 21, an information input section 34 for inputting/outputting data, and an information storage section 36 for storing the same data as the data stored in the information storage section 18, wirelessly synchronizes the data stored in the information storage section 18 with the data stored in the information storage section 36 and outputs the data stored in the information storage section 36 to an information display section 35 on request of the information input section 34.