The present invention relates to an outer diameter pipe forming apparatus for buoys, a buoy using the same, and a method for manufacturing the same, and more particularly, to provide a molding apparatus for continuously molding a cylindrical outer diameter pipe for forming a buoy by supplying three straight members. The buoys are supplied to fill the inside of the outer diameter tube and filled with a side cap, and both ends are closed with side caps, and then the corners where the outer diameter tube and the side caps meet are coated with a welding member to weld the buoys to be used for various purposes. The present invention relates to an outer diameter pipe forming apparatus, a buoy using the same, and a manufacturing method thereof. The present invention is provided with an extrusion apparatus for melt-feeding polyethylene so as to extrude the member from the extrusion unit, and a winding apparatus for cooling the member and feeding it spirally to the winding roller to be formed into a cylindrical shape, the molded cylindrical tube is predetermined Consisting of a cutting device for cutting to the length of； An extrusion nozzle unit in which first, second and third nozzles are formed at the front end of the extrusion unit and the first, second and third members are extruded； A joint roller which presses and fixes the tip of the second, third and third members so as to overlap each other in the winding apparatus in which the winding rollers in which the first, second and third members are spirally supplied are installed； The first, second, and third members overlap and cut the outer diameter tube to be formed smoothly, the cutting body installed in the LM guide and the cutting body transfer cylinder is connected, the motor mounting table is installed with a cutting motor connected to the cutting blade In the buoy outer tube forming apparatus consisting of a cutting device connected to the motor feed cylinder and guides the movement in the feed guide shaft after
