A refrigerator, wherein the refrigerator comprises: a cooler in a freezing loop, the cooler being configured to cool air supplied via an air supply passageway to a storage chamber (13, 14, 15 16, 17); a cooling chamber equipped with the cooler and formed with an air supply port communicated with the storage chamber (13, 14, 15 16, 17); a blower fan configured to feed the air supplied through the air supply port to the storage chamber (13, 14, 15 16, 17); a shielding device at least partially occluding the air supply port; and a control device configured to control acts of the freezing loop, the blower fan and the shielding device, the shielding device comprises: a fan cover configured to cover the blower fan from an outside of the cooling chamber; a driving shaft configured to drive the fan cover to open and close; a screw mechanism formed between the driving shaft and the fan cover; and an electric motor configure to rotate the driving shaft, in a case an environment in the storage chamber (13, 14, 15 16, 17) is in an abnormal state, the control device decelerates the electric motor; characterized in that the refrigerator further comprises: a temperature sensor configured to measure a temperature in the storage chamber (13, 14, 15 16, 17); and a timer configured to measure a time period in which the freezing loop cools the storage chamber (13, 14, 15 16, 17), in a case where the temperature in the storage chamber (13, 14, 15 16, 17) measured by the temperature sensor becomes above a given temperature, or in a case where a continuous operation duration of the freezing loop measured by the timer is above a given duration, the control device decelerates the electric motor. a cooler in a freezing loop, the cooler being configured to cool air supplied via an air supply passageway to a storage chamber (13, 14, 15 16, 17); a cooling chamber equipped with the cooler and formed with an air supply port communicated with the storage chamber (13, 14, 15 16, 17); a blower fan configured to feed the air supplied through the air supply port to the storage chamber (13, 14, 15 16, 17); a shielding device at least partially occluding the air supply port; and a control device configured to control acts of the freezing loop, the blower fan and the shielding device, the shielding device comprises: a fan cover configured to cover the blower fan from an outside of the cooling chamber; a driving shaft configured to drive the fan cover to open and close; a screw mechanism formed between the driving shaft and the fan cover; and an electric motor configure to rotate the driving shaft, in a case an environment in the storage chamber (13, 14, 15 16, 17) is in an abnormal state, the control device decelerates the electric motor; characterized in that the refrigerator further comprises: a temperature sensor configured to measure a temperature in the storage chamber (13, 14, 15 16, 17); and a timer configured to measure a time period in which the freezing loop cools the storage chamber (13, 14, 15 16, 17), in a case where the temperature in the storage chamber (13, 14, 15 16, 17) measured by the temperature sensor becomes above a given temperature, or in a case where a continuous operation duration of the freezing loop measured by the timer is above a given duration, the control device decelerates the electric motor. a fan cover configured to cover the blower fan from an outside of the cooling chamber; a driving shaft configured to drive the fan cover to open and close; a screw mechanism formed between the driving shaft and the fan cover; and an electric motor configure to rotate the driving shaft, in a case an environment in the storage chamber (13, 14, 15 16, 17) is in an abnormal state, the control device decelerates the electric motor; characterized in that the refrigerator further comprises: a temperature sensor configured to measure a temperature in the storage chamber (13, 14, 15 16, 17); and a timer configured to measure a time period in which the freezing loop cools the storage chamber (13, 14, 15 16, 17), in a case where the temperature in the storage chamber (13, 14, 15 16, 17) measured by the temperature sensor becomes above a given temperature, or in a case where a continuous operation duration of the freezing loop measured by the timer is above a given duration, the control device decelerates the electric motor. a temperature sensor configured to measure a temperature in the storage chamber (13, 14, 15 16, 17); and a timer configured to measure a time period in which the freezing loop cools the storage chamber (13, 14, 15 16, 17), in a case where the temperature in the storage chamber (13, 14, 15 16, 17) measured by the temperature sensor becomes above a given temperature, or in a case where a continuous operation duration of the freezing loop measured by the timer is above a given duration, the control device decelerates the electric motor.