a die casting accordingly by manufacturing only the lower cover 120 of aluminum alloy the tub 30 can be prevented from being deformed and at the same time the manufacturing costs of the drying duct 100 can be saved the radiation mechanism 200 is disposed at the upper side of the drying duct 100 to radiate the heat of the drying duct 100 as shown in fig2 the radiation mechanism 200 includes at least one radiation fin preferably a plurality of radiation fins 210 the radiation fins 210 are arranged at a predetermined interval to be normal to a length direction of the drying duct 100 of course the radiation fins 210 may be arranged in the length direction of the drying duct 100 these fins 210 as applied in a combined drum type drying and washing machine increases a radiation area for radiating heat of the drying duct 100 in the course of drying cycle in more detail when the drying duct 100 is heated by a drying operation some of heat is transferred to the lower cover 120 and is radiated and the others of the heat are transferred to the upper cover 110 and are radiated from the upper cover 110 at this time the upper cover 110 having the increased radiation area due to the radiation fins 210 can radiate a large amount of heat as a consequence a very small amount of heat is transferred to the lower cover 120 and the tub thereby preventing the tub 30 from being deformed alternatively the radiation fin 210 may be attached on the upper cover 110 as an independent member or be formed integrally.