Endoscopic insertion aid, endoscopic system, and method of inserting insertion portion of endoscope into body cavity by use of endoscopic insertion aid

An endoscopic insertion aid includes a tube member, a pipeline and a plurality of balloons. The tube member allows an insertion section of an endoscope to be inserted therethrough, and guides the longitudinal movement of the insertion section. The pipeline is provided in the tube member, and communicates with a supply/discharge unit to supply a fluid to or discharge the fluid from the distal end of the tube member. The balloons are disposed on the outer periphery of the distal end of the tube member longitudinally along the tube member, communicate with the pipeline, and inflate/deflate in accordance with the supply/discharge of the fluid via the pipeline. The balloon disposed on the distal side of the tube member is inflated to have an outside diameter larger than that of the balloon disposed closer to the proximal side than the balloon disposed on the distal side when the balloons are inflated.