An electronic device and a hinge assembly thereof are provided. The hinge assembly includes a first and a second fixed block, a first and a second polyline rod, a damper rod and a fastener. The first fixed block has a first and a second end, the second fixed block has a third and a fourth end, and the first polyline rod has a fifth and a sixth end, wherein the fifth end is connected to the second end, and the sixth end is connected to the fourth end. The second polyline rod has a seventh connected to the fourth end, and an eighth end, connected to the second end and the sixth end. The damper rod is slidably disposed on the first fixed block, the fastener is fixed to the first fixed block, and a distal end of the damper rod is fastened into the fastener.