A hinge assembly includes a guiding rail, at least one protruding block, a slidable element, and a rotatable element. The guiding rail includes a first side and a second side surface opposite to each other. The guiding rail further includes a first edge and a second edge in parallel to a longitudinal direction of the guiding rail. The protruding block is disposed on the first side surface. The width of the protruding block is smaller than that of the first side surface, and a gap exists between the protruding block and the first edge. The slidable element includes a sliding surface and a guiding surface opposite to each other. The first edge of the guiding rail inserts into a chute formed on the sliding surface to move the slidable element along the first edge. The rotatable element is pivoted to the slidable element to rotate on the slidable element.