A dryer according to the present disclosure may be a dryer to which a heat pump system is applied, and may provide a structure in which constant temperature external air is suctioned and supplied to a drum to maintain constant performance of the dryer. An air supply unit configured to supply hot dry air to the drum is isolated from an inside of the main body such that internal air including a foreign material is not introduced into the air supply unit, and a suction port cover is separably coupled to the dryer such that a foreign material introduced with the external air is easily removed.