To improve the following-up ability to a load of a refrigerating plant which is equipped with a compressor that is driven by controlling an inverter and the capacity of which is controlled so that the suction pressure of the compressor may become lower than a capacity-up pressure and higher than the capacity-down pressure lower than the capacity-up pressure to a load.

A refrigerating plant is provided with a control means which reads the changing tendency of the suction pressure of the compressor and, when the suction pressure shows a decreasing tendency even when the present suction pressure is higher than the capacity-up pressure, maintains the present operating capacity. When the present suction pressure is lower than the capacity- down pressure and the suction pressure shows an increasing tendency, the control means controls the compressor to maintain the present operating capacity.