A motor assembly has a motor having a rotor and a stator. An impeller is connected to a rotary shaft of the rotor and a housing is disposed between the impeller and the motor and surrounding an upper side of the motor. A diffuser discharges air, which is suctioned by the impeller, along an outer surface of the housing. A heat dissipation cover covers an outer surface of the motor. The heat dissipation cover includes an inner cover spaced apart from the outer surface of the motor and forming an inside-cover flow channel that air flows through and an outer cover having a diameter greater than that of the inner cover and forming an outside-cover flow channel through which air flows along the outer surface thereof.