A balloon (76) is provided at a tip of a body (61) of an overtube with a balloon (11). Air holes (90, 91) are respectively provided at nearest front and rear of the balloon. The air holes are passed through an accommodation hole (70) from an outer surface of the body and they are connected each other through the accommodation hole. The accommodation hole constitutes a connection path (92) for connecting the air holes. The air at rear of the balloon compressed by pulling an S-shape colon passes through the accommodation hole from the air hole at the rear side and the air is exhausted to the front of the balloon from the front air hole. Air at the front of the balloon is suctioned from a forceps tube (50) of an electronic endoscope (10) by driving a suction device (55). Operability of the overtube with the balloon can be increased without adding extra parts and modifying the endoscope.
