A fan includes an impeller having a plurality of blades. Each of the plurality of blades has a trailing edge portion positioned rearmost in a rotation direction and a leading edge portion positioned foremost in the rotation direction. A curved line interconnects the trailing edge portion and the leading edge portion at the shortest distance on an imaginary cylindrical surface. Each of the blades includes a lower surface facing downward in the direction of the center axis and an upper surface facing upward in the direction of the center axis. In the fan, L1/L2 decreases from a radial inner side toward a radial outer side, where L1 denotes the longest distance on the imaginary cylindrical surface between the curved line and a camber line and L2 denotes a length of the curved line.