A treatment tool for an endoscope which is transendoscopically inserted into a body cavity for use, and which includes: a sheath at least partially composed of mixed material in which thermoplastic resin and a crosslinking promoter are mixed； a manipulation wire inserted through the aforementioned sheath so as to be capable of advancing and retracting； a treatment part attached to a first end of the aforementioned manipulation wire； and a manipulation part attached to a second end of the aforementioned manipulation wire； wherein said sheath has a crosslinked part where said thermoplastic resin is crosslinked by irradiating said mixed material with ionizing radiation, and a non-crosslinked region where said thermoplastic resin is not crosslinked.
