A flexible display device and method of manufacturing the same are disclosed. In one aspect, the flexible display device includes a flexible substrate including a first surface and a second surface opposite to the first surface and a display unit over the first surface of the flexible substrate. The flexible display device also includes a first barrier layer over the second surface of the flexible substrate and a first material layer between the first barrier layer and the flexible substrate, wherein the first material layer includes metal. The flexible display device can be more easily manufactured and resistant to external moisture permeation.