To solve such a problem with an electric fan having a fan inserted into a shaft of D-shape in cross section that, when the rotation of the fan is locked by foreign matter, a lock current flows to melt an insulation cover on the wiring of a motor and a interlayer short circuit may occur in the wiring.

The round bar-like shaft 21 is press-fitted to the resin fan 1 and both are connected to each other. The connection conditions of the shaft 21 and the fan 1 are set so that a transmittable torque from the shaft 21 to the fan 1 is lowered according to a rise in temperature of the shaft 21 and, before the insulation cover on the winding 22 of the motor 2 is molten by the lock of the motor 2, the transmittable torque is lowered to less than the lock torque of the motor 2. By this, when the rotation of the fan 1 is locked, the transmittable torque is lowered to less than the lock toque and a slip occurs between the shaft 21 and the fan 1, and the motor 2 moves to a generally no- load operation. As a result, the motor 2 is prevented from being broken.