A freezing and cold storage device (1) and a defrosting control method therefor. The freezing and cold storage device (1) comprises a box body (100) and a door body (200). At least one storage chamber, an air supply passage for supplying cooling airflow to the storage chamber, a return air passage which is used for the airflow from the storage chamber to flow by, a cooling chamber (40) with an air supply opening portion and an air return opening portion and accommodating an evaporator (41), a fan (42) and a defrosting heater (43) and a defrosting air return passage (60) communicating the air supply opening portion and the air return opening portion of the cooling chamber (40) are defined in the box body (100). The air supply passage and the defrosting air return passage (60) are separately internally provided with an air supply valve and a defrosting air return valve (61) so as to selectively switch on and/or block the air supply passage and the defrosting air return passage (60). The defrosting control method comprises the steps of receiving a defrosting signal, starting a defrosting heater (43) disposed on an evaporator (41), closing an air supply valve, and opening a defrosting air return valve (61) so as to enable heat generated by the defrosting to circularly defrost the evaporator (41).