A lifting device configured to adjustably hold a display device at a certain height includes a support frame configured to support the display device, a shaft, a toothed gear, and a rack secured on the support frame. The shaft includes a wide portion secured on the display device and a narrow portion carrying the toothed gear, friction between the wide portion and the narrow portion being sufficient to hold the static weight of the display device. The toothed gear meshes with the rack. An upward or downward push on the display device drives the gear to move up and down along the rack to adjust the height of the display device.