A centrifugal compressor comprising: an impeller configured to be rotated about a main shaft ; a return channel including a return vane for guiding a main stream of a fluid to be compressed by the impeller from an outer side of the main shaft in a radial direction toward an inner side in the radial direction with respect to the impeller ; a plurality of stages of compressor units connected to a downstream side of the return channel and including a first bent channel for changing a direction of the main stream to a direction along the main shaft ; and an intermediate suction channel connected to the return channel in at least one of the plurality of stages of compressor units to merge a suctioned fluid to the main stream, wherein the intermediate suction channel includes a chamber which has a scroll shape in a view from an axial direction of the main shaft and through which the suctioned fluid suctioned from a suction port for suctioning the fluid passes, includes an inlet guide vane for guiding the fluid suctioned from the suction port and passing through the chamber to the impeller , and includes a partitioning wall by which the intermediate suction channel is partitioned from the return channel , and the inlet guide vane is integrated with the return vane in the connected return channel , characterized in that a thickness of the partitioning wall in the direction along the main shaft is thinner from the outer side in the radial direction toward the inner side in the radial direction, in a sectional view along the main shaft so as to have a wedge shape, and the partitioning wall is not interposed between the inlet guide vane and the return vane ; a radial inner end of the partitioning wall is positioned at a center of the return vanes in the radial direction. an impeller configured to be rotated about a main shaft ; a return channel including a return vane for guiding a main stream of a fluid to be compressed by the impeller from an outer side of the main shaft in a radial direction toward an inner side in the radial direction with respect to the impeller ; a plurality of stages of compressor units connected to a downstream side of the return channel and including a first bent channel for changing a direction of the main stream to a direction along the main shaft ; and an intermediate suction channel connected to the return channel in at least one of the plurality of stages of compressor units to merge a suctioned fluid to the main stream, wherein the intermediate suction channel includes a chamber which has a scroll shape in a view from an axial direction of the main shaft and through which the suctioned fluid suctioned from a suction port for suctioning the fluid passes, includes an inlet guide vane for guiding the fluid suctioned from the suction port and passing through the chamber to the impeller , and includes a partitioning wall by which the intermediate suction channel is partitioned from the return channel , and the inlet guide vane is integrated with the return vane in the connected return channel , characterized in that a thickness of the partitioning wall in the direction along the main shaft is thinner from the outer side in the radial direction toward the inner side in the radial direction, in a sectional view along the main shaft so as to have a wedge shape, and the partitioning wall is not interposed between the inlet guide vane and the return vane ; a radial inner end of the partitioning wall is positioned at a center of the return vanes in the radial direction. <EOS>