To provide an axial flow fan capable of improving blowing characteristics and noise characteristics.SOLUTION: An axial flow fan 1 includes an impeller 3 to be rotated around a center shaft extending vertically, a motor, and a housing 4, the motor having a stator and a rotor 24, the impeller having a plurality of vanes 32 arrayed on the radial outer face of an impeller cup 31 fixed to the rotor, the housing having a motor base part 41 supporting the stator at the lower side of the motor, a cylinder part 42 arranged on the radial outside of the impeller, a first rib 43 connecting the motor base part and the cylinder part at the lower sides of the vanes, and a second rib 44 connected to the first rib and having an annular shape with the center shaft as a center, the vanes each having a downward protruded vane first region 322 at the lower edge, the second rib having a radial inner end 441 arranged on the radial outside further than a lower end 3223 of the vane first region.SELECTED DRAWING: Figure 5
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