A retractor has a rigid piercing tube and an expansion body. The expansion body has an introduction tube which is received within the piercing tube, a movable wire which is received within the introduction tube, and stationary wires which are arranged around the movable wire. The proximal end of each of the stationary wires is affixed to the distal end of the introduction tube. The distal end of each of the stationary wires is joined to the distal end of the movable wire. The respective proximal ends of the piercing tube, the introduction tube, and the movable wire are respectively joined to first, second, and third grip sections.
