A centrifugal fan is provided. The centrifugal fan includes a shaft and a plurality of blades. The blades is disposed on the shaft and surround the shaft, and outer edges of the blades define a circle. The circle includes an outer region adjacent to a boundary of the circle, each of the blades includes a first contour line and a second contour line within the outer region, and the neighboring blades include an air channel therebetween, which expands toward the outer edges of the blades according to an interval expanding ratio.