A flat panel display device and a manufacturing method thereof are provided. The flat panel display device includes: a display unit on a substrate; and a sealing structure on the substrate covering the display unit to seal the display unit, the sealing structure including at least one first layer including an inorganic material and at least one second layer including an organic material. The sealing structure includes at least one micro gap, and the micro gap includes an identification material including a fluorescent substance or a dye.