AXIAL FAN

PROBLEM TO BE SOLVED: To provide an axial fan for preventing the occurrence of a crack in an interface surface with a rotor yoke of an inner peripheral wall in a heat cycle, as a result of being capable of efficiently radiating heat, without confining the heat inside an impeller, by improving an impeller structure, in the axial fan of integrally molding the impeller by insert molding of the rotor yoke.SOLUTION: A plurality of blades 7 extending outward in the radial direction from an outer peripheral surface of a hub 6, are formed by resin molding on an outer peripheral surface of a cylinder part 4a of the rotor yoke 4. The hub 6 is formed with an inner peripheral wall 8 and an outer peripheral wall 10, and a groove 9 having the length substantially equal to the length to a bottom surface part 4b from an end surface 4d of the cylinder part 4a of the rotor yoke 4 is formed between the inner peripheral wall 8 and the outer peripheral wall 10. The inner peripheral wall 8 and the outer peripheral wall 10 are joined by a plurality of ribs 11, and the hub 6 covers the end surface 4d of the rotor yoke 4 and a corner part 4f of the rotor yoke so as to sandwich the rotor yoke 4 in the axial direction except for an inner peripheral surface 4g and a bottom surface part 4b of the rotor yoke 4.