Provided is a position-detecting device, etc. that are capable of detecting the position of a capsule endoscope with higher precision than in the past while limiting computational complexity. An information-processing device (6) is provided with: a location region-acquiring unit (621) that determines distances between each of multiple receiving antennas and the capsule endoscope on the basis of the respective reception intensities of the signals received by the receiving antennas and acquires a region in which at least two of multiple spheres, which have the respective receiving antennas as the centers and the distances corresponding to the respective receiving antennas as the radii, overlap an orientation-estimating unit (622) that estimates the orientation of the capsule endoscope at each of multiple points in the region on the basis of the positional relationships between each point and each receiving antenna and of the reception intensities of the signals received by the respective receiving antennas and a position-determining unit (623) that determines the position of the capsule endoscope in the subject on the basis of the position and the orientation of the capsule endoscope at each point.Linvention concerne un dispositif de détection de position, etc., qui sont aptes à détecter la position dun endoscope à capsule avec une précision supérieure à celle du passé, tout en limitant la complexité informatique. Un dispositif de traitement dinformations (6) comporte : une unité dacquisition de région demplacement (621) qui détermine des distances entre chacune des multiples antennes de réception et lendoscope à capsule, sur la base des intensités de réception respectives des signaux reçus par les antennes de réception, et acquiert une région dans laquelle au moins deux des multiples sphères, qui ont les antennes de réception respectives comme centres et les distances correspondant aux antennes de réception respectives comme rayons, se chevauchent une unité destimat
