A The flexible tube insertion apparatus includes: a flexible tube section divided into one or more segments； one or more variable stiffness sections to change bending stiffness of the flexible tube section in a segment unit； a state detector to detect information on a bending state of the flexible tube section； a bend determination section to determine whether the flexible tube section bends based on the detected bending state； and a stiffness controller to control the bending stiffness of the flexible tube section in at least one segment unit by changing a bending stiffness value of the variable stiffness section based on information acquired from the bend determination section. After the bend determination section determines that a segment including the variable stiffness section bends, the stiffness controller controls the variable stiffness section so that a bending stiffness value of the flexible tube section in the segment becomes relatively high to a bending stiffness value of the flexible tube section at a proximal end side from the segment.
