An endoscope includes: a coil spring which is helically wound around an outer periphery of a treatment instrument channel disposed in an insertion section, the coil spring including a distal end which is fixed to the insertion section on a distal end portion side with respect to a bending portion; and a slide member disposed on a proximal end side of the coil spring, the slide member provided for applying an operation force for deforming the coil spring so as to increase a bending strength of at least a portion of the coil spring corresponding to the inside of the bending portion.