A flexible tube insertion apparatus includes a tubular insertion section, a variable stiffness section that causes change of bending stiffness of the insertion section, in regard to continuous segments defined in an axial direction of the insertion section, on a segment-by-segment basis, and a stiffness connecting portion. The stiffness connecting portion is arranged across at least a pair of adjacent segments of the segments. The stiffness connecting portion causes change of bending stiffness of a portion between the pair of segments in such a manner that the bending stiffness of the portion between the pair of segments is continuous with bending stiffness of the pair of segments, in accordance with change of the bending stiffness of the portion between the pair of segments by the variable stiffness section.
