A flexible display device includes a flexible display panel and a window member. The flexible display device includes a folding area and a peripheral area disposed adjacent to the folding area. The window member includes at least first and second base layers. The second base layer is overlapped with the first base layer and has a modulus of elasticity that is higher than that of the first base layer. A thickness of a first portion of the first base layer, which is overlapped with the folding area, is greater than a thickness of a second portion of the first base layer, which is overlapped with the peripheral area.