First and second axial fans are coaxially connected to each other. Each axial fan includes an impeller rotatable about a center axis; a motor rotating the impeller about the center axis, a housing member surrounding the impeller and having a hollow body and approximately square flanges at axial ends of the body, and a group of wires electrically connected to the motor. The axial fans are joined together with their flanges coincident with each other as seen along the center axis. The housing member is provided with first and second receiving portions at least one flange on a center-axis side of an outer periphery of the flange. The groups of wires of the axial fans are pulled out therefrom and extend axially toward a side of the first axial fan opposite to the second axial fan, with passing through the first and second receiving portions, respectively.