A motor assembly for a washing machine including: a stator core having teeth formed along the outer peripheral surface; upper and lower insulators coupled to the upper and lower portions of the stator core to surround the top and underside of the stator core; a first fastening rib protruding from the inner peripheral surface of the lower insulator; a second fastening rib protruding from the inner peripheral surface of the upper insulator to be coupled on the underside thereof to the top of the first fastening rib; and a round-shaped third fastening rib having the underside coupled to the top of the second fastening rib and the top protruding from the top of the upper insulator to be coupled to the underside of a housing in which various parts such as a brake drum and the like are mounted.
