A refrigeration and air conditioning apparatus having circularly connected a compressor, a room heat exchanger, a first expansion valve, and an outdoor heat exchanger, for supplying hot heat from the room heat exchanger, the refrigeration and air conditioning apparatus comprising: a first internal heat exchanger for exchanging without using an intermediate pressure receiver heat of refrigerant existing between the room heat exchanger and the first expansion valve with heat of refrigerant existing between the outdoor heat exchanger and the compressor, the first internal heat exchanger being configured to exchange heat of a high-pressure refrigerant liquid flowing out of the room heat exchanger with heat of the refrigerant sucked into the compressor; an injection circuit for bypassing part of the refrigerant existing between the room heat exchanger and the first expansion valve so as to inject it into a compression chamber within the compressor: a third expansion valve for injection provided along the injection circuit; a second internal heat exchanger for exchanging heat of refrigerant reduced in pressure by the third expansion valve with heat of the refrigerant existing between the room heat exchanger and the first expansion valve, wherein the injection circuit branches from between the first internal heat exchanger and the second internal heat exchanger; characterized in that the refrigeration and air conditioning apparatus further comprises: a temperature sensor arranged on discharge side of the compressor; and a measurement control unit configured to increase an opening degree of the third expansion valve when a discharge temperature of the refrigerant discharged from the compressor detected by the temperature sensor is larger than a target value set in advance, and decrease the opening degree of the third expansion valve when the discharge temperature detected by the temperature sensor is smaller than the target value. a first internal heat exchanger for exchanging without using an intermediate pressure receiver heat of refrigerant existing between the room heat exchanger and the first expansion valve with heat of refrigerant existing between the outdoor heat exchanger and the compressor, the first internal heat exchanger being configured to exchange heat of a high-pressure refrigerant liquid flowing out of the room heat exchanger with heat of the refrigerant sucked into the compressor; an injection circuit for bypassing part of the refrigerant existing between the room heat exchanger and the first expansion valve so as to inject it into a compression chamber within the compressor: a third expansion valve for injection provided along the injection circuit; a second internal heat exchanger for exchanging heat of refrigerant reduced in pressure by the third expansion valve with heat of the refrigerant existing between the room heat exchanger and the first expansion valve, wherein the injection circuit branches from between the first internal heat exchanger and the second internal heat exchanger; a third expansion valve for injection provided along the injection circuit; a second internal heat exchanger for exchanging heat of refrigerant reduced in pressure by the third expansion valve with heat of the refrigerant existing between the room heat exchanger and the first expansion valve, wherein the injection circuit branches from between the first internal heat exchanger and the second internal heat exchanger; characterized in that the refrigeration and air conditioning apparatus further comprises: a temperature sensor arranged on discharge side of the compressor; and a measurement control unit configured to increase an opening degree of the third expansion valve when a discharge temperature of the refrigerant discharged from the compressor detected by the temperature sensor is larger than a target value set in advance, and decrease the opening degree of the third expansion valve when the discharge temperature detected by the temperature sensor is smaller than the target value. a temperature sensor arranged on discharge side of the compressor; and a measurement control unit configured to increase an opening degree of the third expansion valve when a discharge temperature of the refrigerant discharged from the compressor detected by the temperature sensor is larger than a target value set in advance, and decrease the opening degree of the third expansion valve when the discharge temperature detected by the temperature sensor is smaller than the target value.