The accurate position detection without being affected by an unnecessary second magnetic field can be realized by calculating the unnecessary second magnetic field induced and generated at positions of magnetic field sensors by a guiding coil arranged the position detection area of the medical device due to an action of a first magnetic field generated by a magnetic field generator, at the time of position detection, and the second magnetic field is subtracted from the first magnetic field detected by the magnetic field sensors to calculate corrected magnetic-field information. Further, LUTs that store beforehand numerical information having a correlation with the second magnetic field induced and generated at the positions of magnetic field sensors are used to calculate the second magnetic field, thereby enabling to reduce an amount of calculation performed each time and realize high speed processing.
