A flexible display device includes a rolling assembly and a flexible display module. The rolling assembly includes a shaft and at least a shell layer coupled to each other and collectively allowing for formation of a cross-sectional curve based on a characteristic of an Archimedes spiral. The rolling assembly rotates in a direction of releasing or retracting the flexible display module along with processes of expanding and retracting the flexible display module, in order to release or return to a linked state of the shell layer and the shaft and to prevent mechanical scratches caused by overlap of the flexible display module from occurring.