A washing machine includes a drum; a discharging duct communicating with the drum, and discharging inner air of the drum; a supplying duct communicating with the drum, and supplying external air into the drum to make a flow direction of the external air pass across that of the inner air; and a heat exchanger connected to the discharging and supplying ducts, in which a first air flow path which passes therethrough the inner air discharged outward through the discharging duct and a second air flow path which passes therethrough the external air supplied into the drum through the supplying duct cross each other. The washing machine may also include a humidity regulating part which reduces the humidity of the inner air as it is discharged. Thus, the washing machine improves efficiency of heat exchange between the inner air and the external air through the heat exchanger.