A frame structure includes a frame body and fixing structures. The frame structure has an inner edge, an end edge and an outer edge. The fixing structures are disposed on two opposite sides of the frame body respectively, wherein each fixing structure includes a first protrusion, a second protrusion and a stopper portion. One end of the first protrusion or one end of the second protrusion connects to the inner and the end edges to form a containing cavity. The stopper portion is located inside the containing cavity and arranged in parallel to the first and the second protrusions. The lengths of the first and the second protrusions are respectively “L1” and “L2”. The overlap length between the stopper portion and the first protrusion is “α,” the overlap length between the stopper portion and the second protrusion is “b,” L1>α≧0, and L2>β≧0.