A fastening device includes a resilient clamping member and a holder cup respectively stopped at opposing inner wall and outer wall of a support structure, a rubber female connector accommodated in the holder cup, a fastening member adjustably inserted through the rubber female connector, the holder cup and the resilient clamping member to control the relatively clamping position between the resilient clamping member and the holder cup, and a male connector fastened to a decorative ornamental panel and detachably fastenable to the rubber female connector.