In an IC card 30 is sealed an IC chip 70 provided with an exposure sensor 84. When exposure sensor 84 detects that IC card 30 has been opened, exposure sensor 84 outputs an exposure detection signal to a CPU 76. In response to the exposure detection signal, CPU 76 provides a predetermined operation, such as erasure of data in a non-volatile memory 78. As such, the data in non-volatile memory 78 cannot be obtained if IC card 30 is improperly opened to check the data in non-volatile memory 78. Thus the IC card can obtain an enhanced data security.