A protective sheath includes a first cover portion, a flexible display unit, a second cover portion, a flexible portion, and a control unit. The first cover portion includes an external surface portion having an opening and an internal surface portion. The flexible display unit is sandwiched between the external and internal surface portions. A second display surface of the flexible display unit is exposed by the opening. The second cover portion has two bending openings. The second cover portion is bent along the bending openings to be divided into a leaning portion and a supporting portion. Two opposite sides of the flexible portion are foldably connected to the first cover portion and the supporting portion of the second cover portion. The control unit is disposed in an accommodating space of the supporting portion and electrically connected to the flexible display unit.