[Problem] To facilitate ease in maintaining a surgical field as a surgeon sees fit, to facilitate flexibly maintaining and changing the surgical field based on a surgical site or the situation of an operation, and to simplify moving to a required position of the surgical site and post-operative extraction. [Solution] Provided is a retractor 1 which, in small-incision endoscopic surgery, retains an incision site within a body in an open state and maintains an operating field. The retractor 1 comprises a rectangular substrate 2, which is a thin plate composed of tin having 99.9% or higher purity, and which is long and thin when in an extended state. It is possible to insert the retractor 1 within the body via a small incision, and to easily deliver the retractor 1 with a surgical instrument to an incision site within the body, in the rectangular extended form or a tightly rolled-up form. By fitting the retractor 1 into the incision site within the body in a form in which said retractor 1 has been bent and deformed into a required shape with the surgical instrument, it is possible to retain the incision site in the open state so as to maintain the operating field. Given that the substrate 2 is composed of tin having 99.9% or higher purity, the retractor 1 is particularly flexible, and it is possible to easily bend and deform the substrate 2 into a required form using the surgical instrument.Le problème adressé par la présente invention est de faciliter la maintenance d'un champ chirurgical tel qu'un chirurgien le juge approprié, de faciliter la maintenance et le changement flexibles du champ chirurgical sur la base d'un site chirurgical ou de la situation d'une opération, et de simplifier le déplacement vers une position requise du site chirurgical et d'une extraction postopératoire. L'invention concerne un rétracteur 1 qui, en chirurgie endoscopique à petite incision, maintient un site d'incision à l'intérieur d'un corps dans un état ouvert et maintient un champ opéra
