A retractor including an excluding portion having an obtuse distal end, an introduction portion extending from the excluding portion, and a handle portion provided at a proximal end of the introduction portion. The excluding portion and the introduction portion each have an outer diameter that allows insertion into a treatment instrument channel of an endoscope. The excluding portion is configured by a movable wire and a plurality of fixed wires, the movable wire extends through the introduction portion, proximal ends of the fixed wires are fixed to a distal end of the introduction portion, and a distal end of the movable wire and distal ends of the fixed wires are joined to each other. A proximal end of the movable wire is pulled with the handle portion toward the handle portion so the excluding portion develops a cocoon shape. The retractor is useful in minimally-invasive surgery.