A centrifugal compressor casing, comprising a bundle which rotatably supports a rotating shaft, and an impeller fixed to the rotating shaft and that rotates with the rotating shaft about an axis of the rotating shaft, and in which an annular suction flow channel centered on the axis introduces fluid into the flow channel of the impeller, and an annular discharge flow channel centered on the axis that discharges the fluid from the flow channel of the impeller, are formed; a casing main body which covers the bundle from the outer circumferential side; and a volute piece which is provided on an inner surface of the casing main body in the discharge flow channel.