A foldable electronic device including a first body, a second body, a flexible display disposed on the first and the second bodies, a hinge assembly connected between the first and the second bodies, an extension chain assembly, and a linkage is provided. The first and the second bodies are rotated relatively to be unfolded or folded via the hinge assembly. An end of the linkage and an end of the extension chain assembly are pivoted together and coupled to the first body in a sliding and pivoting manner. Another end of the linkage is pivoted to the hinge assembly, and another end of the extension chain assembly is pivoted to the second body. In a transforming process between the folded and the unfolded states, an extension traveling of the extension chain assembly compensates a size difference of the flexible display between the folded and the unfolded states.