The present invention relates to a curtain wall. One end of a sleeve is attached to a vertical bar, and a vertical bar fixing screw is connected to a screw connection unit of the sleeve and the vertical bar so that the sleeve is fixed to the vertical bar. After the other end of the sleeve is inserted into one end of a horizontal bar, a horizontal bar fixing screw is connected to one end of the sleeve and the horizontal bar so that the vertical bar, the sleeve, and the horizontal bar are fixed. The horizontal bar is inserted into the corresponding end of the sleeve, and four sides of the sleeve is attached to and supported by the corresponding inner surface of the horizontal bar. A corresponding vertical surface of a connection unit, which is a rest surface of the sleeve, is supported by one side of a supporting protrusion unit of the horizontal bar, and a horizontal surface of the connection unit is supported on a guide protrusion unit of the horizontal bar. Therefore, four sides of the sleeve is supported on the corresponding surface of the horizontal bar, and sides and a plane of the connection unit of the sleeve is supported on the connection unit of the horizontal bar and a guide protrusion unit so that the sleeve and the horizontal bar are stably supported. The horizontal bar and the vertical bar are simply and stably assembled by the sleeve. The whole horizontal bar and the whole sleeve are stably connected only by screwing one side of the sleeve and the horizontal bar with the guide protrusion units and guide grooves so that man hours for an assembly work are minimized, and a connection force is increased.