A centrifugal fan includes a fan frame, a stator assembly and an impeller. The fan frame has a base plate portion, a cover plate portion and a lateral wall portion. The cover plate portion includes first and second faces. The cover plate portion includes an air inlet, and the lateral wall portion includes an air outlet. The impeller has a radial rotational range. The cover plate portion includes an air-guiding section and an enlarged guiding section. The air-guiding section is aligned with the radial rotational range, and the enlarged guiding section is aligned with an area outside the radial rotational range. A part of the second face is spaced from a bottom of the base plate portion by a first minimal axial distance, and another part of the second face is spaced from the bottom by a second minimal axial distance smaller than the first minimal axial distance.