An edge portion of an endoscope inserting portion includes an observation optical system, a first treatment-tool oscillating base which guides, in a first direction, a first treatment tool guided via a first channel for inserting the treatment tool, and a second treatment-tool oscillating base which guides, in a second direction, a second treatment tool guided via a second channel for inserting the treatment tool. Upon endoscope treatment for the lesion portion using the first and second treatment tools which are projected from the edge openings of two first and second channels for inserting the treatment tool and which are guided by the two first and second treatment-tool oscillating bases, one of the first and second treatment tools is moved to the outside of a field of view of an endoscope image as needed.