An axial flow fan unit includes a first and a second axial flow fan. The first axial flow fan includes a first motor, a plurality of first lead lines connected to the first motor, a first impeller rotatable about a center axis by the first motor, and a first housing arranged to enclose the first motor and the first impeller, wherein the first housing has a first recess portion extending from an inside to an outside of the first housing. Likewise, the second axial flow fan includes a second motor, a plurality of second lead lines, a second impeller, and the second housing, wherein the second housing has a second recess portion extending from an inside to an outside of the second housing. The first and the second lead lines are led out from the first and the second housings through the first and the second recesses, respectively. Further, the first recess portion is deviated relative to or partially overlapped with the second recess portion along a circumferential direction.