An axial flow fan motor having an impeller molded integrally with a shaft from a synthetic resin. The shaft is easily assembled with a bearing arrangement by being brought into tight contact with the inner ring of the bearing arrangement and is reliably fixed thereto in the elastic region of the shaft. A through hole is formed in the shaft along its central axis. After the shaft is fit into the inner ring of the bearing arrangement, a metal pin is pressed into the axial through hole. Because the pin is pressed in, the shaft is elastically expanded and brought into tight contact with the inner ring and fixed thereto in the elastic region of the shaft. Furthermore, the distal end portion of the shaft elastically outwardly expands and is pressed against the end surface of the inner ring, thereby preventing the bearing arrangement from coming off the shaft.