cannot be satisfactorily obtained by the centrifugal compressor disclosed in ptl 1 it is possible to secure a wide operating range by providing a vaneless diffuser in an upstream stage having a high machine mach number when the rotational speed of the impeller the outer diameter of the impeller and the speed of sound are assumed to be n d and a respectively a machine mach number m is a value calculated by expression 1 when the temperature of a gas the specific heat ratio of a gas and a gas constant are assumed to be t u03ba and r respectively the speed of sound can be calculated by expression 2 that is it is possible to eliminate a limitation to the operating range specified by the vanes by providing a vaneless diffuser in an upstream compressor stage having a high machine mach number and thus it is possible to secure a wide operating range it is possible to maintain high efficiency by providing a vaned diffuser in a downstream stage having a narrow width of a flow path that is it is possible to increase the pressure of the fluid g by the vane 29 of the diffuser channel 19 in this configuration it is possible.