One embodiment of the present invention is an insertion apparatus including a flexible insert section inserted into an insertion target and a curved-shape detection sensor which detects a curved shape of the insert section. The curved-shape detection sensor includes at least a core, a cladding, a coating, and a sensing part mechanically attached to the core and detecting the curved shape. The optical fiber is disposed at least in the insert section. The optical fiber includes at least one displacement restraint section which directly or indirectly restrains a displacement of the sensing part relative to the insert section.
