To provide a centrifugal blower formed in a simple structure and reduced in blowing noise and a noise-reduced air conditioner therewith.

A centrifugal blower has an impeller 10 formed with a hub 11, a shroud 12 opposed at a preset space to the hub and plural vanes 13 stranded between the outer periphery of the hub and the outer periphery of the shroud and radially arranged around the axial center of the hub. The rear edges 13b of the vanes are formed in saw-tooth shape to be extended to the cross direction of vanes while being alternately bent in the longitudinal direction of the vanes. In such a structure, the long portions and the short portions of the vanes alternately exist at the rear edges, so that an air flow on the pressure face sides of the vanes and an air flow on the negative pressure face sides are gradually combined at the rear edges in steps throughout the length at the rear edges. As a result, the pressure gradient and speed defect of the air flow following combination are reduced, the disturbance of the air flow at the rear edges is restricted and blowing noise is reduced.