A buffer device has a plate, a moveable ring, and an elastic member. The plate has an insertion hole formed through the plate, a connecting portion, and a retaining hole. The connecting portion and the retaining hole are formed on the plate and are located above the insertion hole of the plate. The moveable ring is moveably mounted out of a front side of the plate and has a slot. The slot is formed through the moveable ring. The elastic member is connected with the connecting portion of the plate and the moveable ring. A top section of the elastic member is wound on the connecting portion of the plate. A bottom section of the elastic member is wound on a top section of the moveable ring and passes through the slot of the moveable ring.