IC CARD

PROBLEM TO BE SOLVED: To provide an IC card whose security can be improved. SOLUTION: At the time of transition from a normal mode to a test mode, second reading data D2 supplied from an I/O terminal 3 through a CPU and CPU controlling part 7 and a non-volatile memory 17 by an IC card issuer are neciphered based on first writing data D1 used at the time of transition from the test mode to the normal mode by a reading part 13 having a decoding function and an enciphering circuit. The enciphered second writing data K2/D2 are communicated through the CPU and CPU controlling part 7 and the I/O terminal 3 to the IC card issuer. The IC card issuer communicates the enciphered second writing data K2/D2 to an IC card supplier. A logic circuit 15 having a non-volatile memory compares the enciphered second wiring data K2/D2 supplied from the IC card supplier through the I/O terminal 3 with the enciphered second writing data K2/D2 from the reading part 13, and when they are made coincident, the transition of an IC card to the test mode is operated, and a symbol indicating the transition to the test mode is recorded.