A flexible display device, which has a bending area and a non-bending area, includes a display panel, and a window member disposed on the display panel and including a first glass substrate, a second glass substrate disposed opposite to the second glass substrate, and a bonding layer disposed between the first glass substrate and the second glass substrate. The bonding layer includes a first bonding part overlapping the bending area and a second bonding part overlapping the non-bending area and having a modulus greater than a modulus of the first bonding part.