To provide an ultra low temperature single-stage compression freezing device that can generate an evaporating temperature of ultralow -40°C or lower using a single-stage scroll compressor.

In this ultralow temperature single-stage compression freezing device including a second circuit 7 for injecting part of liquid refrigerant from a condenser 2 to an intermediate pressure component in a compressing step of a scroll compressor 1 and liquid injection volume controlling means 5 formed on a second circuit 7, the means 5 is controlled in accordance with a temperature of refrigerant compressed by the compressor 1 and cooled a motor 1b, the temperature detected by a temperature sensor 9b. An evaporating temperature of ultralow -40°C or less can be generated using the simple-step compressor 1.