Disclosed are a large cantilever oblique outer eave face plate reverse mounting device and a manufacturing method. The large cantilever oblique outer eave face plate reverse mounting device comprises two upper guide rails, a cantilever steel frame, lower guide rails and a moving platform. the two upper guide rails are parallelly arranged on the top of a cantilever oblique outer eave in a spaced mode in the transverse direction; the cantilever steel frame is mounted on the upper guide rails and slidably connected with the upper guide rails; the front end of the cantilever exceeds the front end of the cantilever oblique outer eave; the lower guide rails are longitudinally connected on structural columns under the cantilever oblique outer eave and close to the connecting positions of the cantilever oblique outer eave and the structural columns; the moving platform is parallel to the bottom face of the cantilever oblique outer eave and arranged below the cantilever oblique outer eave along the transverse pass length; and the front end of the moving platform exceeds the front end of the cantilever oblique outer eave and is hung on the cantilever steel frame through a sling, and the tail end of the moving platform is slidably connected on the lower guide rails. The technical problems that the process is complex, the difficulty of frame body erecting is high, the danger coefficient is large, and the construction quality is not easy to guarantee in the traditional method that a hanging basket or a cantilever frame is used for construction are solved.