Abstract: In an impeller for centrifugal compressors comprising a plurality of blades each having a base end attached to a central hub, each of the blades is given with a thickness which increases progressively toward a hub end thereof, and a suction surface side of the blade is given with a greater thickness increase rate with respect to a neutral plane than a pressure surface side of the blade. Thereby, the inter-blade channel is narrowed locally in the region near the hub end of the suction surface of each blade, and this locally reduces the aerodynamic loading on the blade. In particular, the surge property is improved, and the generation of radially outwardly directed secondary flows can be minimized. This allows the distribution of aerodynamic loading in the radial direction or from the tip end to the hub end of each blade to be controlled at will, and enables the optimum design of the impeller.