An outdoor unit of an air conditioner, the outdoor unit comprising: a cabinet including perimeter surfaces disposed vertically in four directions, respectively, and an upper surface disposed on an upper side thereof that is perpendicular to each of the perimeter surfaces, with suction ports (18a, 20a, 22a) and a discharge port, the suction ports (18a, 20a, 22a) being formed in two surfaces that are formed in a first direction (Le) and a second direction (Ri) opposite to each other and one surface that is formed in a third direction perpendicular to the first direction (Le) and the second direction (Ri), respectively, among the perimeter surfaces, and the discharge port being formed in the upper surface; a heat exchanger disposed inside the cabinet where the suction ports (18a, 20a, 22a) are formed to exchange heat between air introduced into the cabinet and a refrigerant; an air blowing fan disposed inside the cabinet where the discharge port is formed to allow the air that is heat-exchanged by the heat exchanger to flow toward the discharge port; and an orifice disposed along an outer circumference of the air blowing fan, while being spaced apart from the air blowing fan, to form a flow path of the air flowing by the air blowing fan, wherein the orifice includes: a narrowing portion into which the air flowing inside the cabinet is introduced, with the flow path therein having a cross-sectional area that decreases in an air flow direction; a maintaining portion disposed downstream of the narrowing portion, with the flow path therein having a cross-sectional area that is maintained in the air flow direction; and an expanding portion disposed downstream of the maintaining portion, with the flow path therein having a cross-sectional area that increases in the air flow direction, and characterized in that the maintaining portion has a height that decreases from a fourth side opposite to a third side toward the third side along a circumferential surface of the orifice, wherein the third side is provided in the third direction, and an overall height of the orifice defined by the narrowing portion, the maintaining portion and the expanding portion in an up-down direction is equal when seen from the first, second, third and fourth directions. a cabinet including perimeter surfaces disposed vertically in four directions, respectively, and an upper surface disposed on an upper side thereof that is perpendicular to each of the perimeter surfaces, with suction ports (18a, 20a, 22a) and a discharge port, the suction ports (18a, 20a, 22a) being formed in two surfaces that are formed in a first direction (Le) and a second direction (Ri) opposite to each other and one surface that is formed in a third direction perpendicular to the first direction (Le) and the second direction (Ri), respectively, among the perimeter surfaces, and the discharge port being formed in the upper surface; a heat exchanger disposed inside the cabinet where the suction ports (18a, 20a, 22a) are formed to exchange heat between air introduced into the cabinet and a refrigerant; an air blowing fan disposed inside the cabinet where the discharge port is formed to allow the air that is heat-exchanged by the heat exchanger to flow toward the discharge port; and an orifice disposed along an outer circumference of the air blowing fan, while being spaced apart from the air blowing fan, to form a flow path of the air flowing by the air blowing fan, wherein the orifice includes: a narrowing portion into which the air flowing inside the cabinet is introduced, with the flow path therein having a cross-sectional area that decreases in an air flow direction; a maintaining portion disposed downstream of the narrowing portion, with the flow path therein having a cross-sectional area that is maintained in the air flow direction; and an expanding portion disposed downstream of the maintaining portion, with the flow path therein having a cross-sectional area that increases in the air flow direction, and characterized in that the maintaining portion has a height that decreases from a fourth side opposite to a third side toward the third side along a circumferential surface of the orifice, wherein the third side is provided in the third direction, and an overall height of the orifice defined by the narrowing portion, the maintaining portion and the expanding portion in an up-down direction is equal when seen from the first, second, third and fourth directions. a narrowing portion into which the air flowing inside the cabinet is introduced, with the flow path therein having a cross-sectional area that decreases in an air flow direction; a maintaining portion disposed downstream of the narrowing portion, with the flow path therein having a cross-sectional area that is maintained in the air flow direction; and an expanding portion disposed downstream of the maintaining portion, with the flow path therein having a cross-sectional area that increases in the air flow direction, and characterized in that the maintaining portion has a height that decreases from a fourth side opposite to a third side toward the third side along a circumferential surface of the orifice, wherein the third side is provided in the third direction, and an overall height of the orifice defined by the narrowing portion, the maintaining portion and the expanding portion in an up-down direction is equal when seen from the first, second, third and fourth directions.