Disclosed is a manufacturing device for extruding a thin film. The device is used for processing of annular downward extrusion of a water-cooling cast thin film. The device comprises an extrusion port die for forming a plastic film bubble, a water inlet ring for cooling and forming a film bubble, a water return ring for recycling cooling water, a guide structure for pressing a film bubble into a folded film, and a driving mechanism for continuous forming of a blown film, wherein the foregoing parts are sequentially arranged from top down. A vacuum film bubble stabilizer used for forming a certain degree of vacuum on a part of an annular outer surface of a film bubble is provided between the water return ring and the guide structure, a cavity is provided in the vacuum film bubble stabilizer, meshes in communication with the cavity are provided on an inner annular surface of the vacuum film bubble stabilizer, an exhaust tube in communication with the cavity is provided on an annular wall of the vacuum film bubble stabilizer, and the exhaust tube is located on an external end of the annular wall and is connected with a vacuum pump. Due to the presence of the vacuum film bubble stabilizer in the device, the film bubble has good stability, the processing operation is simple and convenient, the quality of a thin film is improved, and the materials required for processing is reduced.