A position detection system for a detection object and a position detection method for a detection object that enable calibration without removing a detection object after the detection object is introduced into a detection space are provided. Provided are a magnetic-field generating unit (3) that generates a position-detection magnetic field; a detection object (5) including a resonant circuit (21) that generates a resonant magnetic field and an external-signal switch that connects or disconnects the path of the resonant circuit (21); a switch-controlling unit (7) that controls connecting or disconnecting of the external-signal switch; a position-detection-magnetic-field detecting unit (9) that detects the magnetic field strength of at least one of the position-detection magnetic field and the resonant magnetic field; and a position-calculating unit (11) that calculates the position and orientation of the detection object (5) based on a detection signal from the position-detection-magnetic-field detecting unit (9).