A centrifugal fan includes a housing and an impeller. The housing includes a sidewall, and the sidewall includes a tongue portion. The impeller includes a fan hub and a plurality of blades. The fan hub is rotatably disposed in the housing, and the tongue portion has an inner contour line on a reference plane. The blades connect to the fan hub. Each one of the blades has an end surface facing the sidewall. The end surface has an outer contour line on the section of the blade. Any two adjacent blades have different outer contour lines. The outer contour line of at least one first blade of the plurality of blades is parallel to the inner contour line. The outer contour line of at least one second blade of the plurality of blades is not parallel to the inner contour line.