An endoscope includes an insertion portion provided with a controllable curved tube. The controllable curved tube includes a plurality of circular tube sections connected in series. A first C-shaped engaging portion is arranged at one end of each tube section. A first included angle is formed between the opening direction of the first C-shaped engaging portion and the axial direction of the tube section to which the first C-shaped engaging portion belongs. A first C-shaped notch is arranged around the outside of the first C-shaped engaging portion. The other end of the tube section is provided with a second C-shaped engaging portion that is engaged with the first C-shaped notch of another tube section. The inner side of the second C-shaped engaging portion is provided with a second C-shaped notch and a spherical protrusion which are engaged with a first C-shaped engaging portion of another tube section.
