A probe shape detection apparatus includes first and second magnetic field detection sections that detect a magnetic field emitted from a magnetic field generation element provided in a longitudinal direction of an elongated probe as magnetic field components in mutually orthogonal three axial directions and output a magnetic field detection signal in accordance with an electromotive voltage group generated when the magnetic field components are detected, a candidate vector calculation section that calculates a candidate vector indicating the orientation of the magnetic field generation element based on the electromotive voltage group generated in the first magnetic field detection section and one piece of candidate position information, an estimated electromotive voltage calculation section that calculates an estimated electromotive voltage based on the one piece of candidate position information and the candidate vector and an estimated position acquiring section that acquires a candidate position that minimizes an error between the electromotive voltage group generated in the second magnetic field detection section and the estimated electromotive voltage as an estimated position of the magnetic field generation element.
