PURPOSE: To prevent reduction of a pressure during switching or a turbo compressor from unload switching control to constant wind pressure control by a method wherein a relation between the upper and lower limit control pressures of a turbo compressor and the upper and lower limit control pressures of a volume compressor is set to a given range.

CONSTITUTION: A compressor equipment comprises two turbo compressors 10 and 20 and the screw compressors 30 and 40 of a volume compressor; a receiver tank 2 for storage of gas fed with a pressure therefrom; and a number of turbo compressors control panel 1. When the upper and lower limit control pressures of the set pressures (the delivery pressures) of the turbo compressors 10 and 20 are P4 and P2 and the upper and lower limit control pressures of the set pressures (the delivery pressures) of the screw compressors 30 ad 40 are P3 and P1, setting is effected so that a relation of P4>P3>P2>P1 is established. This constitution detects a forced feed pressure on a load and performs control of the control pressure of the turbo compressors to a constant value according to the operation state of the volume compressor without interfering control. Thus, a loss owing to blow-off of the turbo compressor is prevented from incurring and the running cost of the equipment is reduced.