Disclosed is a dryer or a washer dryer, including at least a clothes drying system, where the clothes drying system includes a heating structure and a condensing structure; the condensing structure is arranged on a lower part of the dryer or the washer dryer; the condensing structure includes an air inlet and an air outlet for hot air, and further includes a gas inlet and a gas outlet for cold air, and a heat exchanger is arranged inside the condensing structure; the heat exchanger is composed of fins which are superposed in a longitudinal-transverse alternating manner, and a frame with an enclosure structure is arranged outside the heat exchanger.