PROBLEM TO BE SOLVED: To provide a tube body structure constituted such that a built-in material can easily be stored in a predetermined position within an outer sheath tube with excellent workability, the stored position of the content material can be confirmed, and a tip member can easily and surely be fixed within a tip of the outer sheath tube with excellent workability, and also to provide a method for assembling the tube body structure.SOLUTION: A tube body structure comprises: an elongated outer sheath tube 5 a built-in material 10 stored within the outer sheath tube 5 and a tip member 15, which is fixed within a tip 5s of the outer sheath tube 5, and which is, after the fixation, disposed with a front half part 15a projecting forward with respect to the tip 5s, and has an open hole 15h along a longitudinal axis direction S for closing the opening of the tip 5s. The built-in material 10 is fixed with a tip side part 10a engaged with an inner peripheral surface 15n formed by the open hole 15h, thereby defining its position in a longitudinal axis direction S within the outer sheath tube 5.
