<p>A centrifugal compressor having a wide operating range, being economically efficient and high reliability in terms of a stable operation is provided. A centrifugal compressor including a partition wall 37 for dividing a flow channel in the diffuser section 15 and the volute section 16 into a plurality of channels in the direction of circulation of the fluid so as to define a hub-side flow channel A and a shroud-side flow channel B; and a flow rate adjusting valve 36 for lowering the flow rate of the fluid flowing in the shroud-side flow channel B to increase the flow rate in the hub-side flow channel A when the flow rate of the fluid compressed by an impeller 13 is low and not lowering the flow rate of the fluid flowing the shroud-side flow channel B to allow the fluid to flow both in the shroud-side flow channel B and the hub-side flow channel A when the flow rate of the fluid compressed by the impeller 13 is high is employed. Fig. 1A</p>
