A washing and drying machine has a treatment tub and comprises: a washing circuit for drawing liquid from the tub and conveying it back into the tub, having a pump and means for heating the liquid; a drying circuit for extracting air from the tub and conveying it back into the tub, having a first fan, means for dehumidifying the air, and means for heating the dehumidified air; and a heat-pump arrangement having a refrigerating circuit for a refrigerant fluid, which includes a first condenser, a first evaporator, a first lamination valve, and a compressor. The means for heating the liquid comprise the first condenser, and the refrigerating circuit further comprises a second condenser, in series to the first condenser, and a second evaporator. The means for dehumidifying the air comprise the second evaporator, and the means for heating the dehumidified air comprise the second condenser.