Disclosed are a treatment device for an endoscope, an endoscope, and an expanding stent (42). The treatment device for an endoscope comprises: a first electrode comprising an electric treatment part and an operating wire (20)； a second electrode provided in the endoscope, the second electrode comprising a first electrically conductive part (51) and a sliding contact part (53) electrically connected to the first electrically conductive part (51), the first electrically conductive part (51) being used for contact with a human body； a sheath (10), with a surface of the sheath (10) being provided with a second electrically conductive part (52), wherein the operating wire (20) passes through the sheath (10), the sheath (10) passes into the endoscope, when the sheath (10) is located at a pre-set position, the sliding contact part (53) is in contact with and electrically connected to the second electrically conductive part (52), and the sheath (10) is in a sliding fit with the sliding contact part (53). The structural design is rational, the cutting speed is fast, the risk of passive electrode burns is low, and the invention has universal suitability.
