A freezing and refrigerating device comprises a box body and a door body. An air supply path supplying cooling air flow to a storage compartment, an air return path enabling the air flow from the storage compartment to pass, a cooling chamber and a defrosting air return path are defined in the box body, wherein the cooling chamber is provided with an air feeding opening part and an air return opening part and contains an evaporator, a blower and a defrosting heater, and the defrosting air return path is communicated with the air feeding opening part and the air return opening part of the cooling chamber. The air supply path and the defrosting air return path are provided with an air supply door and a defrosting air return door respectively. The present invention further provides a defrosting control method of the freezing and refrigerating device.