The helical tube of the flexible tube forms a first loosely wound region that forms the first flexible portion in cooperation with the outer skin, a tightly wound region that forms the second flexible portion, and a third flexible portion. And a change region that changes the bending difficulty of the distal end portion and the proximal end portion, and a second loosely wound region that forms the fourth flexible portion. The change region is arranged between the tightly wound region and the second sparsely wound region in cooperation with the outer skin so that the bending difficulty of the tip portion approaches the bending difficulty of the second flexible portion. The bending difficulty of the base end portion is changed so as to approach the bending difficulty of the fourth flexible portion, and in cooperation with the outer skin in a state of being disposed between the tightly wound region and the first loosely wound region, The bending difficulty of the distal end portion is made closer to the bending difficulty of the first flexible portion, and the bending difficulty of the base end portion is changed to approach the bending difficulty of the second flexible portion.可撓管の螺旋管は、外皮と協働して第１可撓部を形成する第１疎巻き領域と、第２可撓部を形成する密着巻き領域と、第３可撓部を形成し、先端部と基端部の曲げ難さを変化させる変化領域と、第４可撓部を形成する第２疎巻き領域とを有する。変化領域は、密着巻き領域と第２疎巻き領域との間に配設された状態で外皮と協働してその先端部の曲げ難さを第２可撓部の曲げ難さに近づけ、その基端部の曲げ難さを第４可撓部の曲げ難さに近づけるように変化させ、密着巻き領域と第１疎巻き領域との間に配設された状態で外皮と協働してその先端部の曲げ難さを第１可撓部の曲げ難さに近づけ、その基端部の曲げ難さを第２可撓部の曲げ難さに近づけるように変化させている。
