An air conditioner (AC) indoor unit includes a housing having an inlet and an outlet; a heat exchanger arranged inside the housing; a blower fan for sucking in air at the inlet to be subject to heat exchange with the heat exchanger, and discharging the heat-exchanged air out of the outlet; and an air flow control device for controlling an air flow discharged from the outlet by sucking in air around the outlet. The AC indoor unit may control the direction of a discharged air flow without a conventional blade structure, thereby increasing an amount of discharged air, reducing circulation noise, and enabling design differentiation.