PURPOSE: To easily transfer data between IC cards by judging a data transfer direction and transferring data by a connector itself.

CONSTITUTION: An IC card 1a and an IC card 1b are connected through a connector 8. The connector 8 is composed of detectors 9 and 10, CPU11 and a memory 12 and a display part 13. When the card is inserted, CPU11 judges whether or not "0" is written at a personnel memory area B0 of one side card 1a, and when "0" is stored, the card is not a master card. Consequently, next, CPU11 judges whether or not "0" is written at other side card 1b, and when "0" is not written, it is judges whether or not "1" is written, and when "0" and "1" are not written at the card 1b, CPU11 judges that the card 1b is a master card, and data is transferred from the card 1b to the memory area A0 of the card 1a. When data transfer is completed, "1" is written in the memory area B0 of the card 1a, 1 is taken from the personnel of the card 1b, data transfer is completed and a card sampling display is performed at the display part 13.