A hinge assembly can include: a torsion spring; a shaft, which penetrates through the torsion spring; a bushing, coupled to one end of the torsion spring and one side of the shaft; a holder, which is coupled to the other end of the torsion spring; a housing coupled to the holder; and a damper, which is coupled to the shaft, and which may dampen a rotation speed of the shaft. The damper can include: a first case, which is coupled to the shaft to move in linkage with the shaft; a second case, rotatably coupled to the first case; a viscous fluid, placed between the first case and the second case; and a stopper, which is coupled to the housing and configured to restrict the rotation angle of the second case. Thus, a mobile terminal may be unfolded automatically using a few number of parts without requiring energy consumption.