According to one embodiment, a fastening device comprises an object having a through hole, and a fastener which fixes the object to a support by being screwed into a screw hole. The fastener includes a gripper and a stopper. The gripper is capable of protruding outside of the object from the through hole and getting into the through hole, and has an end surface on a side opposite to a male screw portion. The stopper is positioned between the male screw portion and the gripper. In a state in which the male screw portion is screwed into the screw hole, the end surface is positioned inside the through hole. In a state in which the male screw portion is removed from the screw hole, the gripper protrudes outside of the object from the through hole, and the stopper is caught in the object and holds the fastener to the object.