A foldable flexible display device, with a design of disposing reinforcing structures on lower surfaces of a support plate, when a front surface of a flexible display device is subjected to an external impact, the reinforcing structures are able to support the sinking flexible display panel and the displacement of the flexible display device is reduced so that the back cover under the support plate is not in contact with the sinking flexible display panel. This can obviously improve the impact condition of the flexible display panel and the impact resistance of the flexible display panel, thereby preventing the flexible display panel failure caused by stress concentration.