To make it possible to appropriately determine whether refrigerating machine oil is supplied from a compressor oil reservoir to an expansion mechanism via an expander oil supply pipe in a refrigeration device including a refrigerant circuit configured by connecting together a compressor, a heat sink, an expander, and an evaporator.

Between a compressor and an expander, an expander oil supply pipe for supplying refrigerating machine oil from a compressor oil reservoir of the compressor to an expansion mechanism of the expander and an expander oil return pipe for returning the refrigerating machine oil from an expander oil reservoir of the expander to an inlet side of the compressor are connected. It is determined whether the refrigerating machine oil is supplied from the compressor oil reservoir to the expansion mechanism on the basis of an expander oil return temperature that is a temperature of the refrigerating machine oil returning from the expander oil reservoir to the inlet side of the compressor and an evaporation temperature of refrigerant in a refrigerant circuit.