PURPOSE: To reduce fitting dimensions by fitting a projection of a vane boss to the outer surface of a rotor endring.

CONSTITUTION: Projection 14 of vane boss 12 is engaged with the outer surface of rotor endring 13 of a motor, and thereby the fitting dimensions are reduced and at the same time a suspension is eliminated. In consideration of fitting and removal, an angle is provided at the end of vane projection 14. Since a pulling force is needed at the time of removal, for the engagement of the entire surface, projections 14 are provided at several places and also slits 15 are provided. Consequently, it is possible to fit a vane directly to an outer rotor. Hence, it is possible to provide a thin ventilating fan in the direction of the motor shaft so that both a thin and thick type fan can be used. This simplifies the fitting construction.