A refrigeration apparatus comprising: a first circulation circuit including a first compressor, a first condenser, a first expansion device, and a first evaporator sequentially connected by piping to circulate a refrigerant therethrough; a second circulation circuit including a second compressor, a second condenser, a second expansion device, and a second evaporator sequentially connected by piping to circulate a refrigerant therethrough; a cascade capacitor formed of the first evaporator and the second condenser to exchange heat between the refrigerant flowing through the first evaporator and the refrigerant flowing through the second condenser; an opening and closing valve; a plurality of expansion tanks (18a, 18b, 18c) connected to a pipe between the second evaporator and the second compressor via the opening and closing valve; an expansion tank unit; and a controller configured to control the opening and closing valve, wherein the first compressor, the first condenser, the first expansion device, the first evaporator, the second compressor, and the second condenser are mounted in an outdoor unit, wherein the plurality of expansion tanks (18a, 18b, 18c) are mounted in the expansion tank unit, and wherein the controller opens the opening and closing valve if at least one of a pressure on a suction side and a pressure on a discharge side of the second compressor is equal to or higher than a first pressure value, and closes the opening and closing valve if the pressure on the suction side and the pressure on the discharge side of the second compressor are equal to or lower than a second pressure value that is lower than the first pressure value, when the second compressor is stopped, and opens the opening and closing valve for a preset time when the second compressor is restarted. a first circulation circuit including a first compressor, a first condenser, a first expansion device, and a first evaporator sequentially connected by piping to circulate a refrigerant therethrough; a second circulation circuit including a second compressor, a second condenser, a second expansion device, and a second evaporator sequentially connected by piping to circulate a refrigerant therethrough; a cascade capacitor formed of the first evaporator and the second condenser to exchange heat between the refrigerant flowing through the first evaporator and the refrigerant flowing through the second condenser; an opening and closing valve; a plurality of expansion tanks (18a, 18b, 18c) connected to a pipe between the second evaporator and the second compressor via the opening and closing valve; an expansion tank unit; and a controller configured to control the opening and closing valve, wherein the first compressor, the first condenser, the first expansion device, the first evaporator, the second compressor, and the second condenser are mounted in an outdoor unit, wherein the plurality of expansion tanks (18a, 18b, 18c) are mounted in the expansion tank unit, and wherein the controller opens the opening and closing valve if at least one of a pressure on a suction side and a pressure on a discharge side of the second compressor is equal to or higher than a first pressure value, and closes the opening and closing valve if the pressure on the suction side and the pressure on the discharge side of the second compressor are equal to or lower than a second pressure value that is lower than the first pressure value, when the second compressor is stopped, and opens the opening and closing valve for a preset time when the second compressor is restarted. opens the opening and closing valve if at least one of a pressure on a suction side and a pressure on a discharge side of the second compressor is equal to or higher than a first pressure value, and closes the opening and closing valve if the pressure on the suction side and the pressure on the discharge side of the second compressor are equal to or lower than a second pressure value that is lower than the first pressure value, when the second compressor is stopped, and opens the opening and closing valve for a preset time when the second compressor is restarted.