Centrifugal fan

The utility model provides a centrifugal fan comprising an impeller with a central axis in the up and down direction as a center, a motor part driving the impeller to rotate surrounding the central axis and a case shell accommodating the impeller. The case shell is equipped with an upper flat plate part covering the upper side of the impeller, a lower flat plate part covering the lower side of the impeller and fixed to the motor part and a side wall part covering a radial external side of the impeller and forming an air supplying port with the upper flat plate part and the lower flat plate part. A wind tunnel part covering the impeller is formed by the upper flat plate part, the side wall part and the lower flat plate part; A border between the internal side surface of the side wall part and either the lower surface of the upper flat plate part or the upper surface of the lower flat plate part is equipped with a linear rectifying component extending along the border. The rectifying component comprises a recti