An indoor unit including a heat exchanger that cools indoor air sucked through a suction port, a cross flow fan that enables the indoor air to be sucked through the suction port, and enables cold air cooled by the heat exchanger to be discharged into a room through a discharging port, a drainage tray unit that is disposed below the heat exchanger to collect condensate water generated in the heat exchanger, and a blade that is rotatably coupled to the drainage tray unit to open the discharging port, and whose rotary shaft is formed in an upper portion of the discharging port. The drainage tray unit includes a guide unit that prevents the cold air from being discharged to an upper side of the blade so that the cold air is discharged to a lower side of the blade when the blade is opened.