A washing and drying machine comprising: - a cabinet; - a tub mounted in the cabinet; - a drum rotatably provided inside said tub; - a drying duct, having a drying heater and a circulating fan, said drying duct supplying hot air into said drum to dry laundry; and - an air-cooling condensing unit that performs heat exchange between air introduced from the outside of the cabinet and at least a part of said tub to dry air used to dry the laundry in said drum; - wherein said air-cooling condensing unit comprises: -- an inlet port allowing outside air to be introduced into the cabinet; -- an outlet port allowing the outside air, which has passed the tub to be discharged out of the cabinet; said washing and drying machine characterized by further comprising: -- an introduction channel that guides the outside air introduced through said inlet port into said tub; -- a condensing channel for performing heat exchange between the outside air introduced into said tub through said introduction channel and the inner circumferential surface of said tub to dry air used to dry the laundry; -- a discharge channel that guides the heat-exchanged air such that the air is discharged out of the cabinet through said outlet port; and -- a condensing plate mounted in the path of the outside air in the condensing channel to facilitate heat exchange between the outside air and the at least part of said tub; -- wherein said condensing plate is spaced from the inner circumferential surface of said tub such that the outside air can flow along the inner wall of said tub. - a cabinet; - a tub mounted in the cabinet; - a drum rotatably provided inside said tub; - a drying duct, having a drying heater and a circulating fan, said drying duct supplying hot air into said drum to dry laundry; and - an air-cooling condensing unit that performs heat exchange between air introduced from the outside of the cabinet and at least a part of said tub to dry air used to dry the laundry in said drum; - wherein said air-cooling condensing unit comprises: -- an inlet port allowing outside air to be introduced into the cabinet; -- an outlet port allowing the outside air, which has passed the tub to be discharged out of the cabinet; said washing and drying machine characterized by further comprising: -- an introduction channel that guides the outside air introduced through said inlet port into said tub; -- a condensing channel for performing heat exchange between the outside air introduced into said tub through said introduction channel and the inner circumferential surface of said tub to dry air used to dry the laundry; -- a discharge channel that guides the heat-exchanged air such that the air is discharged out of the cabinet through said outlet port; and -- a condensing plate mounted in the path of the outside air in the condensing channel to facilitate heat exchange between the outside air and the at least part of said tub; -- wherein said condensing plate is spaced from the inner circumferential surface of said tub such that the outside air can flow along the inner wall of said tub. -- an inlet port allowing outside air to be introduced into the cabinet; -- an outlet port allowing the outside air, which has passed the tub to be discharged out of the cabinet; said washing and drying machine characterized by further comprising: -- an introduction channel that guides the outside air introduced through said inlet port into said tub; -- a condensing channel for performing heat exchange between the outside air introduced into said tub through said introduction channel and the inner circumferential surface of said tub to dry air used to dry the laundry; -- a discharge channel that guides the heat-exchanged air such that the air is discharged out of the cabinet through said outlet port; and -- a condensing plate mounted in the path of the outside air in the condensing channel to facilitate heat exchange between the outside air and the at least part of said tub; -- wherein said condensing plate is spaced from the inner circumferential surface of said tub such that the outside air can flow along the inner wall of said tub. -- an introduction channel that guides the outside air introduced through said inlet port into said tub; -- a condensing channel for performing heat exchange between the outside air introduced into said tub through said introduction channel and the inner circumferential surface of said tub to dry air used to dry the laundry; -- a discharge channel that guides the heat-exchanged air such that the air is discharged out of the cabinet through said outlet port; and -- a condensing plate mounted in the path of the outside air in the condensing channel to facilitate heat exchange between the outside air and the at least part of said tub; -- wherein said condensing plate is spaced from the inner circumferential surface of said tub such that the outside air can flow along the inner wall of said tub.