A portable telephone to which additional function units, such as a flip unit and a slide unit, that provide additional functions for the main body of a portable telephone, are easily mounted on the case of a basic unit that includes only the essential units required for speech. One or more of an LCD bezel 40, a flip cover 50, a keypad bezel 60, grips 70, a keypad slide cover 80 and a slide cover 90, which are additional function units, are mounted on a basic unit 20. Therefore, this arrangement can cope with a request from a user who desires to alter a portable telephone he or she purchased to obtain a model he or she favors.