Disclosed is a flexible display device capable of forming a display device on a glass substrate and simultaneously ensuring flexibility, and a fabrication method thereof, the method including preparing a glass substrate having a display region and a non-display region defined on a front surface thereof, forming a display device on the display region defined on the front surface of the glass substrate, preparing a metal foil substrate, bonding the metal foil substrate to the glass substrate such that a front surface of the metal foil substrate faces the front surface of the glass substrate so as to seal the display device, attaching a first passivation film on a region of a rear surface of the glass substrate, the region corresponding to a part or all of the non-display region defined on the front surface of the glass substrate, and attaching a second passivation film on an entire rear surface of the metal foil substrate, performing a first etching with respect to the display region of the rear surface of the glass substrate by using the first passivation film as a mask, removing the first passivation film, and performing a second etching with respect to the display region and the non-display region of the rear surface of the glass substrate, removing the second passivation film, and mounting a display device driving unit on the non-display region defined on the front surface of the glass substrate.