There are provided a position detection system, a guidance system, and a position detection method which obviate the need for frequency adjustment of an alternating magnetic field used in position detection of a device and which allow the device to be made more compact and less expensive. There are included a device (capsule endoscope 20) provided with a magnetic induction coil, a drive coil 51 for generating an alternating magnetic field, a plurality of magnetic sensors 52 for detecting an induced magnetic field, a frequency determining section 50B for determining a position calculating frequency based on a resonance frequency of the magnetic induction coil, and a position analyzing unit 50A for calculating, at the position calculating frequency, at least one of the position and the orientation of the device 20 based on the difference between outputs from the magnetic sensors 52 when only the alternating magnetic field is applied and outputs from the magnetic sensors 52 when the alternating magnetic field and the induced magnetic field are applied; and at least one of a frequency range of the alternating magnetic field and an output frequency range of the magnetic field sensors is limited based on the position calculating frequency.