An insertion shape detection apparatus includes an insert portion having flexibility. The insert portion includes a shape estimation section where curved shape is estimated and a shape non-estimation section where curved shape is not estimated. The insertion shape detection apparatus includes a sensing part arranged only in the shape estimation section to detect the curved shape of the shape estimation section. Thus, the number of sensing parts is reduced and the increase in the diameter of the insert portion and complicated processing of curve information is avoided, while the curved shape of the insert portion in a section necessary to assist an endoscopic observation can be detected.
