An improved rotary machine such as centrifugal type compressor adapted to rotate under high load of the type including a plurality of impellers fixedly mounted (shrinkage-fit) on a main shaft. To effectively inhibit the rotor from vibrating due to loosened fitting of the impellers onto the main shaft the improvement consists of each of the impellers being provided with a sleeve portion which is made integral with the impeller. The sleeve portion is located at a position removed from the main part of the impeller along the axial direction of the main shaft with the position being determined in accordance with the theory of strength of materials in such a manner that displacement of the impeller in the radial direction due to centrifugal force resulting from rotation of the rotary machine has no effect on determination of the position of the sleeve portion, wherein the sleeve portion is shrink fit onto the main shaft of the impellers.