A built-in type outdoor unit for a split type air conditioner, comprising: a louver frame (104, 106) divided into a suction area and a discharge area, a plurality of louver blades being installed on the louver frame (104, 106); and an outdoor unit casing having an opened front surface unit contacting the louver frame and being opened to the outside of the building, both side units formed at both ends of the front surface unit, a rear surface unit formed to face the front surface unit, a bottom surface unit formed at the lower ends of the front surface unit and the rear surface unit, and a top surface unit formed at the upper ends of the front surface unit and the rear surface unit, characterized in that the louver frame comprises an external frame for being fixedly installed on an inner wall of an opened space on an outer wall of a building and an internal frame coupled to the external frame, whereby the plurality of lower I blades are installed on the internal frame, and in that the outdoor unit casing is coupled to the louver frame (104, 106), and in that the outdoor unit casing is divided into a suction casing corresponding to the suction area of the louver frame and a discharge casing corresponding to the discharge area of the louver frame, and the discharge casing is coupled to the suction casing, and the suction casing and the discharge casing are linked to each other so as to discharge sucked air, and in that a width of the outdoor unit casing is smaller than that of the inside space of the louver frame (104, 106), and the outdoor unit casing is fixedly coupled to the louver frame (104, 106) by using a special fastening member. a louver frame (104, 106) divided into a suction area and a discharge area, a plurality of louver blades being installed on the louver frame (104, 106); and an outdoor unit casing having an opened front surface unit contacting the louver frame and being opened to the outside of the building, both side units formed at both ends of the front surface unit, a rear surface unit formed to face the front surface unit, a bottom surface unit formed at the lower ends of the front surface unit and the rear surface unit, and a top surface unit formed at the upper ends of the front surface unit and the rear surface unit, characterized in that the louver frame comprises an external frame for being fixedly installed on an inner wall of an opened space on an outer wall of a building and an internal frame coupled to the external frame, whereby the plurality of lower I blades are installed on the internal frame, and in that the outdoor unit casing is coupled to the louver frame (104, 106), and in that the outdoor unit casing is divided into a suction casing corresponding to the suction area of the louver frame and a discharge casing corresponding to the discharge area of the louver frame, and the discharge casing is coupled to the suction casing, and the suction casing and the discharge casing are linked to each other so as to discharge sucked air, and in that a width of the outdoor unit casing is smaller than that of the inside space of the louver frame (104, 106), and the outdoor unit casing is fixedly coupled to the louver frame (104, 106) by using a special fastening member.