An air purifier includes a main body having an inlet and a discharge device mounted on the main body and configured to receive air introduced into the main body through the inlet and discharge the air from the air purifier, wherein the discharge device includes a discharge opening, an opening and closing member including a portion having a size and shape corresponding to the discharge opening, and configured to move out of the discharge opening and into the discharge opening to open and close the discharge opening, and a discharge portion including a plurality of discharge holes, wherein each discharge hole of the plurality of discharge holes has a size smaller than a size of the discharge opening, and wherein the discharge portion has an air discharging area that is variable.