To add a displaying function to an IC card at a low cost without changing the control system of an existent IC card and the system of an existent reader/writer.

A signal line for communication between the reader/writer and a micro-controller (10) is used in common as a signal line for transferring data to a display driver from the micro-controller. A clock signal (CLK1) supplied from the reader/writer is frequency-divided to generate a display clock (CLK2) In reading a file whose display is not permitted, the displaying clock is held in a specific one state to avoid being displayed and outputted. In reading a file whose display is permitted on the other hand, information interpreted to be an error on the side of the reader/writer is added to the prefix of a communication block.