1. An endoscope position detecting apparatus comprising: an endoscope having a flexible insertion part which is insertable into an object to be examined, said endoscope having illumination-light emitting means for emitting an illumination light toward a distal end of said insertion part, and an objection optical system for observing an illuminated subject; a first position estimation element including a magnetic-field generation element for generating a magnetic field to an environment arranged on said insertion part for estimating a position of said first position estimation element by application of a drive signal; a second position estimation element including a magnetic-field detection element for detecting the magnetic field generated by said magnetic-field generation element, said second position estimating element being installed at a known position outside said subject and which is used for estimation of said position of said first position estimation element with respect to said known position; position estimation means for estimating a position of said first position estimation element which is arranged within said insertion part with respect to said known position outside of said subject from a detection signal which is detected by said magnetic-field detection element on the outside of the subject; insertion-part form estimation means for estimating a form of said insertion part which is inserted into said object to be examined from the position which is estimated by said position estimation means; and display means for displaying a form of said insertion part which is estimated by said insertion-part form estimating means, by two images corresponding respectively to cases where directions from an observation point which observes said insertion part are different from one another, wherein said position estimation means initially changes orientation of said magnetic-field generation element to determine a maximum value and a minimum value of the magnetic-field strength which can be detected by said magnetic-field detection element, and sets said maximum value and said minimum value to reference information whenever a distance between said magnetic-field generation element and said magnetic-field detection element is changed, to decide a range in which a distance between said magnetic-field generation element and said magnetic-field detection element exists, with reference to said reference information with respect to the magnetic-field strength determined from the detection signal which is detected by said magnetic-field detection element, to thereby estimate a position of said magnetic-field generation element within said insertion part.