A two-stage refrigeration apparatus comprising: a first refrigeration cycle device including a first refrigerant circuit in which a first compressor, a first condenser, a first expansion device, and a first evaporator are connected by pipes, the first refrigerant circuit circulating a first refrigerant; a second refrigeration cycle device including a second refrigerant circuit in which a second compressor, a second condenser, a receiver, a second expansion device, and a second evaporator are connected by pipes, the second refrigerant circuit circulating a second refrigerant; a cascade condenser including the first evaporator and the second condenser and configured to cause the first refrigerant flowing in the first evaporator and the second refrigerant flowing in the second condenser to exchange heat with each other; a receiver heat exchanging portion configured to cool the receiver by heat exchange with a portion in which the first refrigerant being low-pressure flows in the first refrigerant circuit; a heat-exchanging-portion bypass portion for bypassing the receiver heat exchanging portion in the first refrigerant circuit; a receiver heat-exchanging-portion opening and closing device configured to control passage of the refrigerant through the receiver heat exchanging portion; second-refrigerant-circuit pressure determining means configured to determine a pressure of the second refrigerant in the second refrigerant circuit; and a controller, wherein the controller is configured to perform controlling to activate the first compressor and cause the first refrigerant to flow into the receiver heat exchanging portion when estimating that the second refrigerant will reach a supercritical state when the second compressor is inactive, and to open the receiver outlet opening and closing device on the basis of the pressure of the second refrigerant relating to the determination by the second-refrigerant-circuit pressure determining means when the second compressor is inactive, wherein the second refrigerant circuit further includes a receiver outlet opening and closing device configured to control an outflow of the refrigerant in a liquid state from the receiver, and the controller is configured to perform controlling so as to close the receiver outlet opening and closing device when estimating that the second refrigerant will reach a supercritical state when the second compressor is inactive. a first refrigeration cycle device including a first refrigerant circuit in which a first compressor, a first condenser, a first expansion device, and a first evaporator are connected by pipes, the first refrigerant circuit circulating a first refrigerant; a second refrigeration cycle device including a second refrigerant circuit in which a second compressor, a second condenser, a receiver, a second expansion device, and a second evaporator are connected by pipes, the second refrigerant circuit circulating a second refrigerant; a cascade condenser including the first evaporator and the second condenser and configured to cause the first refrigerant flowing in the first evaporator and the second refrigerant flowing in the second condenser to exchange heat with each other; a receiver heat exchanging portion configured to cool the receiver by heat exchange with a portion in which the first refrigerant being low-pressure flows in the first refrigerant circuit; a heat-exchanging-portion bypass portion for bypassing the receiver heat exchanging portion in the first refrigerant circuit; a receiver heat-exchanging-portion opening and closing device configured to control passage of the refrigerant through the receiver heat exchanging portion; second-refrigerant-circuit pressure determining means configured to determine a pressure of the second refrigerant in the second refrigerant circuit; and a controller, wherein the controller is configured to perform controlling to activate the first compressor and cause the first refrigerant to flow into the receiver heat exchanging portion when estimating that the second refrigerant will reach a supercritical state when the second compressor is inactive, and to open the receiver outlet opening and closing device on the basis of the pressure of the second refrigerant relating to the determination by the second-refrigerant-circuit pressure determining means when the second compressor is inactive, wherein the second refrigerant circuit further includes a receiver outlet opening and closing device configured to control an outflow of the refrigerant in a liquid state from the receiver, and the controller is configured to perform controlling so as to close the receiver outlet opening and closing device when estimating that the second refrigerant will reach a supercritical state when the second compressor is inactive.