A hinge
assembly includes a central shaft (20), including an outer
screw thread (221); a turning element (30), including a central hole (322) and a holding pin (314), an inner
screw thread (323) formed at an inner surface of the central hole; a elastic means (40); a blocking element (50), defining a first through hole (51) and a second through hole (52); and a button (71), including a supporting pin (72). The central shaft extends through the central hole of the turning element, the first elastic element, and the first through hole of the blocking element in that order, the outer
screw thread engages with the inner screw thread, and the holding pin of the turning element is received in the second through hole of the blocking element. The present invention enables a foldable electronic device to be opened simply by pressing the button.