Patent ID: 8052595

Claim:
A position detecting method of detecting a position of a body-insertable apparatus that is introduced into a subject and that moves inside the subject using a predetermined magnetic field for position detection, the method comprising: firstly detecting a strength of the magnetic field for position detection at a predetermined position on an outer surface of the subject by a magnetic field sensor unit fixedly arranged at the predetermined position; controlling the strength of the magnetic field for position detection based on the magnetic field strength detected in the firstly detecting; and secondly detecting a position of the body-insertable apparatus based on the strength of the magnetic field for position detection detected by the body-insertable apparatus after the controlling, wherein the magnetic field for position detection is generated by a coil to which power is supplied by a power supply unit that is constituted of any one of a primary cell and a secondary cell, and the position detecting method further comprises determining whether an amount of retained power that is retained in the power supply unit is sufficient for an amount of a necessary power that is necessary for generating the magnetic field for position detection controlled in the controlling.