PURPOSE: To prevent generation of vibration or noise by forming a step part which makes the entrance angle of an inducer unit discontinuous, on a chip positioned in the radial tip end of the inducer unit, in an impeller on the tip on the air flow-in side of its blade is provided the inducer unit formed by being twisted in the rotational direction.

CONSTITUTION: The impeller 1 of a turbocharger is connected to a rotary shaft not shown in the figure to be turned at a high speed so as to accelerate the air passing a cell between blades 3 projecting from a hub 2 by centrifugal force for supercharging the air to an engine. An inducer unit 4 positioned at the air intake side tips of the blades 3 is formed by being twisted in the rotational direction to be in parallel to flowing direction of flow-in air, thus the speed distribution of the flow at the entrance is uniformalized. In this case, a step part 6 is formed on an inducer chip 5 positioned at the radial tip of the inducer unit 4 of the impeller 1 so as to make the entrance angle of the inducer unit 4 so that the hub 2 side and chip 5 side of the impeller 1 may be prevented from making stall simultaneously.