A propelling unit of a self-propellable apparatus is attached to a front end portion of an insert section of an electronic endoscope. The propelling unit includes feeding rollers disposed at its front. On each feeding roller, one end of a belt is wound. A winding roller and a worm wheel are provided behind each feeding roller. When the worm wheel rotates, the belt is drawn out from the feeding roller, and wound up onto the winding roller. The belts move while making contact with an interior wall of a body lumen, and hence produce propulsive force to the front end portion of the insert section. When the contact between the belts and the interior wall is insufficient, a balloon is inflated to press the belts against the interior wall.
