To obtain a tube manufacturing line wherein a metal strip is easily passed through keeping a straight advancing property from a squeeze roll without a tube body supporting mechanism to a sizing roll, a time until the starting of welding is largely reduced, excellent productibity and workability are obtained and an yield is improved.

This tip guiding tool 20 for manufacturing a welded tube is provided with a conical part 22 having a sharp tip being inserted into a sizing roll in the other end of a cylindrical part 21 having an open end part into which the tip part of a metal strip formed into an open pipe shape is inserted. A clamp 23 is provided inside the cylincirical part 21 in the vicinity of the open end part, and the central part in the width direction of the metal strip is held between the inner surface of the cylindrical part 21 and the arc surface 27a of a clamp member 27. A binding metal fitting 28 such as a hook to which a tow rope 29 is attached is also provided in the tip of the conical part 22. Thus, the metal strip is passed through without depending on manual work by piercing the tip guiding tool 20 attached to the tip of the metal strip into the sizing roll.