A dividing wall member 26 is provided inside a specific bending piece 25 selected from a plurality of bending pieces 25, an internal space of the bending piece 25 is divided by the dividing wall member 26 into a first space 27 that opens corresponding to one rotating shaft 25b, of rotating shafts 25b that form a left and right pair, and a second space 28 that is larger than the first space and opens corresponding to another rotating shaft 25b, of the rotating shafts 25b that form a left and right pair, and rotating shafts 25a that form an upper and lower pair, a signal cable 11a is inserted as a first internal component inside a first space 27, and a pair of light guides 12 and a treatment instrument insertion channel 13 are inserted as second internal components inside the second space 28.
