To inhibit data recorded in an external storage medium such as a memory card by a portable telephone set capable of recording/reading out data in/from the external storage medium from being utilized for a telephone set other than the portable telephone set.

The portable telephone set 10 is provided with a memory card slot 24 allowed to be loaded with a memory card 26. The telephone set 10 can download contents data such as a picture and music by accessing an external contents providing site. In the case of recording the downloaded data in the memory card 26, the telephone number of its own station is inserted into the data and recorded. When the telephone number inserted into the data recorded in the memory card 26 does not coincide with the telephone number of its own station, the reading of the data is inhibited.