PURPOSE: To prevent data from being copied and to improve the holding of secrecy by reading out the shapes and numbers of holes, projections and markings formed on the surface of a memory card, and when the read contents do not coincide with stored ones, inhibiting the reading of data from the card.

CONSTITUTION: A circuit 3 for reading out/writing the contents of data is connected to an IC memory card 1 inserted into a card slot 2a through respective connection parts 6. An IC memory card reader/writer 2 is provided with a judging circuit 5 for the shapes and numbers of holes, projections and markings as a judging means for detecting and judging the fixed shapes and numbers of holes, projections and markings. The circuit 5 is connected to a CPU 4, and when the card 1 is inserted, the shapes and numbers of holes, projections and carved seals formed on the surface of the card 1 are read out by the card reader and the data of the card 1 are ciphered or deciphered in accordance with the shapes. Thereby even if a third person obtains the card 1, said function can prevent the contents of the card 1 from being known.