A semiconductor memory card comprising a control IC 302, a flash memory 303, and a ROM 304. The ROM 304 holds information such as a medium ID 341 unique to the semiconductor memory card. The flash memory 303 includes an authentication memory 332 and a non-authentication memory 331. The authentication memory 332 can be accessed only by external devices which have been affirmatively authenticated. The non-authentication memory 331 can be accessed by external devices whether or not the external devices have been affirmatively authenticated or not. The control IC 302 includes control units 325 and 326, an authentication unit 321 and the like. The control units 325 and 326 control accesses to the authentication memory 332 and the non-authentication memory 331, respectively. The authentication unit 321 executes a mutual authentication with an external device.