The centrifugal turbo-compressor (2) includes a hermetic casing; a drive shaft (6); a first and a second compression stage (12, 13) configured to compress a refrigerant and respectively including a first and a second impeller (18, 19) connected to the drive shaft (6) and being arranged in a back-to-back configuration; an interstage sealing device provided between the first and second impellers (18, 19). The hermetic casing includes a main casing portion (4) in which are arranged the first and second compression stages (12, 13) and the inter-stage sealing device. The first and second compression stage (12, 13) respectively includes a first and a second aerodynamic member (29, 31) each having an annular disc shape and respectively facing front-sides (21, 22) of the first and second impellers (18, 19).