In a laundry washing/drying machine involving drying by a heat pump cycle, in an initial stage of the drying operation the heat within an air circulation path is deficient and therefore it is impossible to effect quick heating of air on a drum inlet side up to a sufficiently high temperature. According to the present invention there is provided a drying unit capable of raising the drum inlet air temperature quickly up to a sufficiently high temperature in an initial stage of the drying operation and thereby shortening the drying time. The drying unit includes a heat pump cycle device for performing a cycle of radiating, with use of a radiator, the heat of a refrigerant compressed by a compressor, passing the refrigerant through a pressure reducing/expansion valve, evaporating the refrigerant in an evaporator and compressing the refrigerant again by the compressor, an air circulation path for allowing air to be circulated by a blower in such a manner that air heated by the radiator is introduced into a drying chamber to dry the laundry, exhaust air discharged from the drying chamber is passed through the evaporator, then is heated again by the radiator and the air thus dehumidified is circulated by the blower, and an external heat source applying device for applying the heat of an external heat source to the evaporator to quicken the rise in temperature of the air in an initial stage of the drying operation.