To avoid the impact of an external force on bearing members and to improve reliability of the life of the bearing members, in particular, ball bearings.

The axial flow fan according to the present invention is configured such that a bearing member to be arranged on a rotor hub is movably held in the axial direction on the inside peripheral surface of a bearing housing in a non-fixed fit state so that the bearing member always abuts against the rotor hub by means of spring members interposed between the bearing member and a barrel-bearing stepped portion of the inside peripheral surface of the bearing housing, and at the same time, a distance between the bottom inside surface of the rotor hub and the tip of a small diameter cylindrical part forming the bearing housing opposed to the bottom inside surface, or a distance between the tip of the cylindrical part of the rotor hub and the tip of the motor supporting part opposed to the tip of the cylindrical part of the rotor hub, is smaller than the movable distance of the bearing member in the bearing housing, and further the distance between the tip of the bearing housing and the bottom inside surface of the rotor hub is smaller than the distance between the bottom inside surface of the rotor hub and other opposed parts of the stator.