An endoscope insertion apparatus is provided that has an inner-side unit in which a plurality of inner-side fixing sections having an inner-side arm are uniformly arranged in a circumferential direction, an outer-side unit in which a plurality of outer-side fixing sections having an outer-side arm are uniformly arranged in a circumferential direction and in which slit portions that extend in a direction perpendicular to the circumferential direction and from which the inner-side arms protrude are uniformly arranged in the circumferential direction between the outer-side fixing sections, and an insertion operation portion that changes a front/rear relationship between the inner-side arms and outer-side arms.
