A driving block includes a plurality of magnetic-field generating elements and a driving signal generating section, and the magnetic field generated by the plurality of magnetic-field generating elements is detected by a plurality of magnetic-field detecting elements. A shape calculating block calculates a shape of an insertion portion of an endoscope based on a frequency component corresponding to a frequency of the driving signal in a detection signal detected by the plurality of magnetic-field detecting elements. Oscillation frequency of the reference clock for deciding the frequency of the driving signal is changeably set by the frequency setting section, and the reference clock with oscillation frequency set by the frequency setting section is supplied to both of the driving block and the shape calculating block.