A serial axial fan includes first and second axial fans. The first axial fan preferably includes a first motor portion, a first impeller, and a first housing. The second axial fan preferably includes a second motor portion, a second impeller, and a second housing. In the first impeller, an angle defined by a rotational plane of the first impeller with a chord of each blade of the first impeller on an imaginary cylindrical surface centered about a central axis increases as the radius of the imaginary cylindrical surface increases.