A propelling unit (40) of a self-propellable apparatus (11) is attached to a front end portion of an insert section (13) of an electronic endoscope (10). The propelling unit (40) includes feeding rollers (56) disposed at its front. On each feeding roller (56), one end of a belt (42) is wound. A winding roller (59) and a worm wheel (57) are provided behind each feeding roller (56). When the worm wheel (57) rotates, the belt (42) is drawn out from the feeding roller (56), and wound up onto the winding roller (59). The belts (42) 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 (13). When the contact between the belts (42) and the interior wall is insufficient, a balloon (43) is inflated to press the belts (42) against the interior wall.
