The guide device for the diffusor at the compressor impeller outlet of a radial compressor has guide blades with stepped inlet edges. The step is implemented by setting back the hub-side inlet edge. This meridional stepping divides the guide blades into two component blades, of which the first component blade is made longer than the second component blade. The set-back of the inlet edge of the hub-side component blade and the associated superposition of the noise fields which are produced on the front and rear inlet edge of the diffusor leads to improvement of the acoustic properties of the compressor.