An air cleaner including a first housing including a first suction port and a first discharge port; a first fan inside the first housing; a coupling duct on an upper portion of the first housing; a second housing including a second suction port and a second discharge port; a second fan inside the second housing; and a coupling base on a lower portion of the second housing and including a guide surface sloping outwardly in an upward direction, wherein the coupling base is separably couplable to the coupling duct. When the coupling base and coupling duct are coupled, a portion of air discharged through the first discharge port is guided by the guide surface and discharged outside of the second housing, and when the coupling base and coupling duct are separated, air is guided by the guide surface into the second housing.