In a refrigeration system (10) that includes a refrigerant circuit (20) configured by connecting a plurality of circuit component parts including a compressor (30), a pressure reduction device (36, 39) and a plurality of heat exchangers (34, 37) and operates in a refrigeration cycle by circulating refrigerant through the refrigerant circuit (20), a refrigerant state detection section (51) is provided for detecting the refrigerant temperatures and entropies at the entrance and exit of each of the compressor (30), the pressure reduction device (36, 39) and the heat exchangers (34, 37), and a variation calculation section (52) is provided that uses the refrigerant temperatures and entropies detected by the refrigerant state detection section (51) to separately calculate the magnitude of energy variation of refrigerant produced in each of the circuit component parts.