Provided is an assist tool that assists the movement of a treatment tool with respect to an endoscope channel, said treatment tool comprising an insertion body that is inserted into the channel. The assist tool comprises: a flexible tube having formed therein an insertion path into which the insertion body of the treatment tool is inserted a connecting section that is provided to the flexible tube and that can be connected to the endoscope such that the channel and the insertion path communicate a first holding section that is provided to the flexible tube and that holds an insertion section of the endoscope or the exterior of an operating section to be attached to the insertion section and a second holding section that is movable with respect to the first holding section and that holds the insertion body of the treatment tool.
