A material dispensing device, a material output volume detecting device, and a related damper device for use in an automated beverage preparation apparatus are disclosed. The material output volume detecting device includes: a damper device arranged to operably buffer liquid material flowing therethrough; and a flowmeter arranged to operably measure the flow of liquid material outputted from the damper device. 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.