A centrifugal turbomachinery in accordance with the present invention can lower a fluid loss in a return flow path. In the centrifugal turbomachinery, a plurality of centrifugal impellers is attached to a rotating shaft, and the centrifugal turbomachinery is provided with a diffuser having a plurality of blades introducing a fluid boosted by a front stage impeller to a rear stage impeller, and a return flow path means. The return flow path means has a side plate arranged in a back surface side of the front stage impeller, a plate opposing the side plate and arranged in a front surface side of the rear stage impeller, and a plurality of blades arranged between the side plate and the plate so as to be spaced in a peripheral direction. A maximum diameter portion of the side plate is changed in the peripheral direction.