An endoscope system includes an overtube (2) and an endoscope (1), where the overtube (2) is equipped with a shape-holding section (2b) capable of shape-holding and relaxing, a balloon (2a) provided at the distal end of the shape-holding section (2b) to fix the overtube (2) to a body cavity, and an endoscope passage hole (13) serving as a conduit through which the endoscope (1) is passed and the endoscope (1) is equipped with a shape-holding section (1b) capable of shape-holding and relaxing and a balloon (1a) provided at the distal end of the shape-holding section (1b) to fix the endoscope (1) to the body cavity. When one of the endoscope (1) and overtube (2) is inserted, the shape-holding section of the other shape-holds, and the body cavity is pulled with the balloon (1a) inflated, making it possible to reduce insertion length.