PURPOSE: To provide a protective pipe, in which neither jamming nor bending of hollow yarn occurs and no trouble such as the catching or the like during automatic conveying, and obtain a method and device for manufacturing the protective pipe.

CONSTITUTION: A plastic sheet S, which is fed by a sheet feeding part 3 from a sheet roll 1 to a sheet cutting part 2, is pushed out to a forming guide part 4, after being cut to a specific width, so as to be fed to a pipe forming part 5 during being rounded in order to lap the opposing end edges of the sheet. At that time, in the pipe forming part 5, the plastic sheet S is fed between a forming mold 51 and a forming rod 57 so as to lap the opposing end edges at the position of the welding horn inserting slit of the forming mold 51 in order to form a hollow yarn bundle lapping pipe with stepless weld by emitting an ultrasonic wave from a welding horn 59, which is inserted through the welding horn inserting slit.