An overtube according to this invention includes: an insertion part (5), that is inserted into a subject and has a lumen (3), through which a device insertion part of a device (endoscope 2) for performing a medical procedure inside a body of the subject is removably inserted, the insertion part being inserted into the subject; a tissue incising part (6) that is disposed at a distal end side of the insertion part so as to cross the lumen and incises a tissue of the subject; a manipulating member (electrode manipulating wires 7A, 7B) which is connected to the tissue incising part and is disposed in a manner enabling advancing and retracting with respect to the insertion part; a manipulating part (electrode manipulating part 8) for manipulating the manipulating member to advance and retract with respect to the lumen; and a needle manipulating part (10) for manipulating a puncture needle (32A, 32B) and a pusher (35).