An electric motor assembly includes an outer housing with two sides open, an impeller provided in the outer housing, an inner housing disposed concentrically in the outer housing and spaced apart from the impeller, a stator provided in the inner housing, a rotor rotatably disposed in the stator, a first air flow path through which air flows in an axial direction between the inner housing and the outer housing based on rotation of the impeller, and a second air flow path through which air is joined with the air of the first air flow path via an inside of the inner housing and a gap between the impeller and the inner housing based on rotation of the impeller. Accordingly, cooling of the stator can be facilitated by the air flow paths.