An introduction apparatus comprising: an insertion section configured to extend along a longitudinal axis and to be able to be inserted into a lumen; a manipulation section disposed on a base end side of the insertion section and configured in such a manner that a rotational driving source is housed in the manipulation section which generates rotational driving force; an inner rotating cylinder provided in the insertion section at any position on the insertion section and annularly configured to be rotatable around the longitudinal axis, the inner rotating cylinder having a plurality of rollers rotatably installed on an outer circumferential surface of the inner rotating cylinder and rotating in accordance with the rotational driving force from the rotational driving source; a covering member that is stretchable and fixed at opposite ends thereof to non-rotating sites located beyond the inner rotating cylinder, an outer rotating cylinder (8, 61) comprising an engagement section including a plurality of circular grooves (8a, 61a) formed at positions corresponding to the plurality of rollers arranged in the inner rotating cylinder, each of the circular grooves (8a, 61a) having a size sufficient to contain a respective roller covered with the covering member, the outer rotating cylinder (8, 61) being fitted on a casing side of the inner rotating cylinder covered with the covering member, such that the rotation of the inner rotating cylinder causes the protruding portions of the cover formed by the plurality of rollers to push the circular grooves (8a, 61a) ahead to rotate the outer rotating cylinder (8, 61); and an introduction propulsion unit rotatable along with the outer rotating cylinder (8, 61) and comprising a spiral propulsion site on an outer surface of the introduction propulsion unit, the introduction propulsion unit supporting rotational introduction into the lumen; characterized in that the covering member is configured to have an inner circumferential length equal to or smaller than an outer circumferential length of the inner rotating cylinder including the plurality of rollers, the covering member annularly covering the inner rotating cylinder including the plurality of rollers in tight contact with the inner rotating cylinder when assembled in a stretched manner, the covering member, when covering the inner rotating cylinder and the plurality of rollers, further configured to contact the inner rotating cylinder with no gap between the cover and the inner rotating cylinder, and to be stretched so as to cover the plurality of rollers with no gap between the covering member and the plurality of rollers. an insertion section configured to extend along a longitudinal axis and to be able to be inserted into a lumen; a manipulation section disposed on a base end side of the insertion section and configured in such a manner that a rotational driving source is housed in the manipulation section which generates rotational driving force; an inner rotating cylinder provided in the insertion section at any position on the insertion section and annularly configured to be rotatable around the longitudinal axis, the inner rotating cylinder having a plurality of rollers rotatably installed on an outer circumferential surface of the inner rotating cylinder and rotating in accordance with the rotational driving force from the rotational driving source; a covering member that is stretchable and fixed at opposite ends thereof to non-rotating sites located beyond the inner rotating cylinder, an outer rotating cylinder (8, 61) comprising an engagement section including a plurality of circular grooves (8a, 61a) formed at positions corresponding to the plurality of rollers arranged in the inner rotating cylinder, each of the circular grooves (8a, 61a) having a size sufficient to contain a respective roller covered with the covering member, the outer rotating cylinder (8, 61) being fitted on a casing side of the inner rotating cylinder covered with the covering member, such that the rotation of the inner rotating cylinder causes the protruding portions of the cover formed by the plurality of rollers to push the circular grooves (8a, 61a) ahead to rotate the outer rotating cylinder (8, 61); and an introduction propulsion unit rotatable along with the outer rotating cylinder (8, 61) and comprising a spiral propulsion site on an outer surface of the introduction propulsion unit, the introduction propulsion unit supporting rotational introduction into the lumen; characterized in that the covering member is configured to have an inner circumferential length equal to or smaller than an outer circumferential length of the inner rotating cylinder including the plurality of rollers, the covering member annularly covering the inner rotating cylinder including the plurality of rollers in tight contact with the inner rotating cylinder when assembled in a stretched manner, the covering member, when covering the inner rotating cylinder and the plurality of rollers, further configured to contact the inner rotating cylinder with no gap between the cover and the inner rotating cylinder, and to be stretched so as to cover the plurality of rollers with no gap between the covering member and the plurality of rollers.