Abstract: An axial flow fan including a rotation shaft section to be mounted on the rotation shaft of rotation drive means, an inner blade group provided outside the rotation shaft section so as to be coaxial therewith, and an outer blade group provided outside the inner blade group so as to be coaxial therewith, wherein the inner blade group is formed of a plurality of inner blades provided radially around the rotation shaft section, the outer blade group is formed of a plurality of outer blades provided radially around the rotation shaft section, and the velocity V1 of the wind generated by the inner blade group and the velocity V2 of the wind generated by the outer blade group have a relationship of 1.5V1<V2 by designing the blades of the inner blade group and the outer blade group with respect to number, area, angle and shape.

Abstract: An axial flow fan including a rotation shaft section to be mounted on the rotation shaft of rotation drive means, an inner blade group provided outside the rotation shaft section so as to be coaxial therewith, and an outer blade group provided outside the inner blade group so as to be coaxial therewith, wherein the inner blade group is formed of a plurality of inner blades provided radially around the rotation shaft section, the outer blade group is formed of a plurality of outer blades provided radially around the rotation shaft section, and the velocity V1 of the wind generated by the inner blade group and the velocity V2 of the wind generated by the outer blade group have a relationship of 1.5V1<V2 by designing the blades of the inner blade group and the outer blade group with respect to number, area, angle and shape.