The information terminal device of the invention has a first function of displaying non-confidential data in a selectable manner on its display screen and, in response to the user's selection of the non-confidential data, showing the details of the non-confidential data. The information terminal device also has a second function of displaying confidential data in a selectable manner and, in response to the user's selection of the confidential data, showing the details of the confidential data. The first function is given as one normally selectable menu option and is activated by the user's selection of the corresponding menu. The second function is, however, not given as a normally selectable menu option and is triggered only by the user's series of operations of an operation unit in a preset sequence. No operation-related display appears on the display screen of the information terminal device during the user's series of operations of the operation unit. The information terminal device of this configuration does not hint even the presence of confidential data to any third person and thus effectively prevents the third person from analyzing or decoding the data stored in the information terminal device and having illegal access to the confidential data. This arrangement of the invention desirably enables the safe handling of confidential data without the potential for leakage of the confidential data from the information terminal device.