PROBLEM TO BE SOLVED: To provide a medical collection bag capable of easily redeveloping a bag that has been closed once, in the body without using another device and being applicable to NOTES (Natural Orifice Translumenal Endoscopic Surgery).SOLUTION: A medical collection bag includes: a bag 10 having a through-hole around an opening part an elastic band 20 inserted into the through-hole of the bag and memorized in such a mode as developing the opening part a flexible outer cylindrical tube 30 storing the bag and the elastic band a flexible connecting cable 40 connected to the elastic band and extended to the outside via the outer cylindrical tube and a redeveloping means, after closing the operation part and the bag once, allowing free development thereof by an external operation. The redeveloping means is formed of a string member 50 whose one end is connected to the bag and whose other end extends to the outside via the outer cylindrical tube, or a partially or totally spring-shaped extending/contracting member 70 whose one end is connected to the bag and whose other end is connected to a connecting cable.
