To facilitate the insertion skill of a large intestine endoscope which is difficult by making a sheath into an automatic movable type, and to enable the insertion to the intestinum ileum and the coelenteron.

A rear balloon 4 is expanded by feeding air from a rear injection tube 5, and a rear balloon base 1 is fixed to an intestinal tract. Air flows into a body section hollow layer 7 from a rear valve hole 18 which has been closed by the retracting of a rear balloon valve 2, the body section of a sheath stretches, and a front movable balloon ring 13 is advanced forward. A front valve hole 20 which has been closed by the traction of an afaront balloon valve 12 by a traction yarn 11 is opened to inflate a front balloon 15, and the front movable balloon ring 13 is fixed to the intestinal tract. Air is vacuumized by a negative pressure by the rear injection tube 5, and the rear balloon 4 is contracted. By the contraction of the body section of the sheath, the rear balloon base 1 is pulled forward and moves in the intestinal tract, and the front balloon 15 contracts to finish the advancing motion. A stopper is provided on an intestinal endoscope fiber, and a large intestine endoscope fiber is advanced deeper along with the advancement of the sheath.