Single port access (SPA) surgery is a laparoscopic procedure using only one transumbilical-placed port. Natural orifice transluminal endoscopic surgery (NOTES) offers the possibility of surgery without visible scars. To address the access and stability problems in SPA and NOTES, we developed a device called rigid-flexible outer sheath. This sheath can be switched between flexible and rigid modes by a novel pneumatic shapelocking mechanism, and it has a double curvature structure that enables it to flex in four directions at the distal end and three directions on the rigid-flexible shaft. The insertion part of the prototype is 300 mm long with a 20 mm outer diameter, and the part is equipped with four working channels. In vivo experiments using a swine show that the outer sheath has high potential for solving access and stability problems. We expect that the outer sheath will be useful for SPA and NOTES.