Disclosed herein is a centrifugal fan. A driving device is connected to an impeller and drives the impeller to rotate within a case. The flowing channel includes a pressure-enhanced section and an output section. The case includes an air input section, an axial inlet section and a radial air outlet. The bottom base has a center and allows the driving device to be secured thereon. Multiple ribs are interconnected between the bottom base and the case to define air inlets among the ribs, the bottom base and the case. The air inlet within the output section has an outmost edge, which is farther from the center than an outmost edge of the air inlet within the pressure-enhanced section, or the air inlet within the output section has an area, which is larger than that of the air inlet within the pressure-enhanced section.