A flexible display device includes a display panel and a plurality of curving-restricting structures. The display panel has a display surface and a bottom surface opposite thereto. The display surface has a visible region and an outer region surrounding the visible region. The curving-restricting structures is disposed on at least one of the outer region of the display surface and the bottom surface of the display panel. Each curving-restricting structure has a top surface and at least a slanted side wall. The top surfaces of adjacent curving-restricting structures are spaced with each other, and the slanted side walls of adjacent curving-restricting structures face each other. When the flexible display device are curved to a predetermined extent, adjacent curving-restricting structures may resist against with each other to prevent the display panel from being unduly curved to be damaged, and thus a use reliability of the flexible display device is improved.