A damper device for use in an automated beverage preparation apparatus is disclosed. The damper device includes: a damper base having a material entrance hole, a material exit hole, and a material buffer chamber positioned between the material entrance hole and the material exit hole; a diaphragm covered on the material buffer chamber; and a fastening element positioned on the diaphragm and having a hollow portion. When the volume of liquid material within the material buffer chamber exceeds a predetermined amount, the diaphragm deforms to protrude outward, so that a part of the diaphragm enters the hollow portion of the fastening element.