The loss of refrigerant pressure which is caused in a return-side interconnecting piping line (19) comprising return-side interconnecting piping lines respectively extending from outlet ports (24, 34, 44) of single-stage side utilization units (12, 13, 14) to an inlet port (61) of a heat source unit (11) is set such that the lowest valued refrigerant pressure loss is caused by a said return-side interconnecting piping line of the return-side interconnecting piping line (19) that is connected to the lowest of the single-stage side utilization units (12, 13, 14) in compartment preset temperature.