In a treatment endoscope which includes: an elongated insertion section having a first channel for inserting a treatment instrument therethrough an arm, having a second channel for inserting a treatment instrument therethrough, attached to the distal end of the insertion section so that the first channel communicates with the second channel a first operation section for operating the arm and a second operation section for operating the insertion section, the arm has a first bending section which can be operated to be bent via the first operation section, the insertion section has a second bending section which can be operated to be bent via the second operation section, and an interlock mechanism connects the first operation section to the second operation section so that, when either one of the first bending section and the second bending section is bent by operating either one of the first operation section and the second operation section, the other one of the first bending section and the second bending section bends.
