An insertion system includes an insertion section and a rigidity variable portion provided in the insertion section. The rigidity variable portion includes a superelastic alloy member whose rigidity starts changing from a high-rigidity state to a low-rigidity state at a temperature, which varies with a degree of bending of the superelastic alloy member, and a heating member capable of switching between presence and absence of heating of the superelastic alloy member. The insertion system also includes a bending state detection sensor that detects a bending state of the rigidity variable portion, and a rigidity variable controller that controls switching between presence and absence of heating of the superelastic alloy member by the heating member to control the temperature of the superelastic alloy member.