1. A centrifugal compressor, comprising:a rotational shaft;
a main casing surrounding at least a part of the rotational shaft, the main casing having an inlet and an outlet separated from each other in an axial direction of the rotational shaft and an annular space surrounding a section of the rotational shaft at a side of the inlet and communicating with the inlet, wherein a fluid to be compressed before compression flows in the annular space;
at least one impeller disposed in a fixed state to the rotational shaft inside the main casing;
a flow guide member disposed inside the annular space and extending along the axial direction of the rotational shaft, the flow guide member having a flow guide element extending along a radial direction of the rotational shaft and having a predetermined blade width in the axial direction of the rotational shaft;
a plurality of injection holes disposed along the flow guide member and separated from one another along the axial direction of the rotational shaft; and
a flow path which extends inside the annular space and through which a cleaning fluid to be supplied to the plurality of injection holes is capable of flowing.