A centrifugal compressor comprising: a rotating shaft which extends in an axial direction; a first impeller which is provided on the rotating shaft; a second impeller which is provided on the rotating shaft and disposed on a downstream side of the first impeller along the axial direction; a return flow path which guides a first fluid flowing to a radially outer side from the first impeller toward a radially inner side; an introduction flow path which introduces the first fluid guided to the radially inner side by the return flow path to the second impeller; a plurality of return vanes provided in the introduction flow path; an intermediate suction flow path which is adjacent to the introduction flow path and additionally supplies a second fluid to the second impeller; a partition wall which is configured to partition the intermediate suction flow path and the introduction flow path in the axial direction; f a plurality of straightening vanes provided on a radially inner side of the intermediate suction flow path; and a curved flow path which is connected to a radially inner side of the introduction flow path and the intermediate suction flow path, extends to be curved from the position connected to the introduction flow path toward the downstream side in the axial direction, and is configured to guide the first fluid and the second fluid to the second impeller; wherein a side surface on an upstream side along the axial direction of the introduction flow path is disposed on the downstream side along the axial direction from an apex position at the radially outermost apex portion of a circumferential surface on the inner circumferential side of the return flow path; a flowing direction of the first fluid matches a flowing direction of the second fluid at a Proposition where the intermediate flow path is connected to the introduction flow path; a position of a radially inner end on the downstream side of the straightening vane in a radial direction is the same as a position of a radially inner end on the downstream side of the return vane in the radial direction, wherein the radial direction is orthogonal to the axial direction; characterized in that the intermediate suction flow path is connected to the radially inner side of the introduction flow path. a rotating shaft which extends in an axial direction; a first impeller which is provided on the rotating shaft; a second impeller which is provided on the rotating shaft and disposed on a downstream side of the first impeller along the axial direction; a return flow path which guides a first fluid flowing to a radially outer side from the first impeller toward a radially inner side; an introduction flow path which introduces the first fluid guided to the radially inner side by the return flow path to the second impeller; a plurality of return vanes provided in the introduction flow path; an intermediate suction flow path which is adjacent to the introduction flow path and additionally supplies a second fluid to the second impeller; a partition wall which is configured to partition the intermediate suction flow path and the introduction flow path in the axial direction; f a plurality of straightening vanes provided on a radially inner side of the intermediate suction flow path; and a curved flow path which is connected to a radially inner side of the introduction flow path and the intermediate suction flow path, extends to be curved from the position connected to the introduction flow path toward the downstream side in the axial direction, and is configured to guide the first fluid and the second fluid to the second impeller; wherein a side surface on an upstream side along the axial direction of the introduction flow path is disposed on the downstream side along the axial direction from an apex position at the radially outermost apex portion of a circumferential surface on the inner circumferential side of the return flow path; a flowing direction of the first fluid matches a flowing direction of the second fluid at a Proposition where the intermediate flow path is connected to the introduction flow path; a position of a radially inner end on the downstream side of the straightening vane in a radial direction is the same as a position of a radially inner end on the downstream side of the return vane in the radial direction, wherein the radial direction is orthogonal to the axial direction; characterized in that the intermediate suction flow path is connected to the radially inner side of the introduction flow path.