An endoscope apparatus includes an endoscope including a flexible insertion tube and a curved-shape detection sensor. The sensor includes an optical fiber that transmits detection light and a sensing part provided in at least a part of the optical fiber, and detects a curved shape of the insertion tube based on a change in characteristics of the detection light passed through the sensing part in accordance with a change in the curved shape of the optical fiber when the optical fiber curves. Apart of the optical fiber or a part of a guide member through which the optical fiber is passed is held to a component having greater torsion stiffness than any other component constituting the insertion tube.
