A position detection device for detecting a position of a capsule endoscope in a subject, the capsule endoscope being introduced into the subject and moving in the subject, based on received strength of signals transmitted from the capsule endoscope at a plurality of receiving antennas (40, 40, 40), the position detection device comprising: a region acquiring unit configured to obtain distances between the receiving antennas and the capsule endoscope based on the received strength of the signals received by the plurality of receiving antennas, and configured to acquire a region where at least two spheres of a plurality of spheres with the receiving antennas as centers and the distances corresponding respectively to the receiving antennas as radii overlap with one another; an orientation estimating unit configured to estimate orientations of the capsule endoscope at a plurality of points in a plurality of sub-regions obtained by dividing the region in a lattice form based on positional relationships between the points and the receiving antennas, and the received strength of the signals received by the receiving antennas; and a position determination unit configured to determine the position of the capsule endoscope in the subject based on the positions of the points and the orientations of the capsule endoscope, wherein the orientation estimating unit is configured to acquire a candidate region of a point at which a vector representing the orientation of the capsule endoscope passes based on a direction of the receiving antenna, a direction from the point to the receiving antenna, and the received strength at the receiving antenna, and is configured to determine a position where the candidate regions of the point at which the vector passes overlap with one another, the candidate regions being acquired respectively for the plurality of receiving antennas, and wherein the position determination unit is configured to calculate theoretical values of the received strength of the signals received by the plurality of receiving antennas based on the positions of the points and the orientations of the capsule endoscope in a case of assuming that the capsule endoscope exists at the points, as well as acquiring measured values of the received strength at the plurality of receiving antennas, and is configured to detect a point having a minimum error between the theoretical value and the measured value as the position of the capsule endoscope out of the plurality of points. a region acquiring unit configured to obtain distances between the receiving antennas and the capsule endoscope based on the received strength of the signals received by the plurality of receiving antennas, and configured to acquire a region where at least two spheres of a plurality of spheres with the receiving antennas as centers and the distances corresponding respectively to the receiving antennas as radii overlap with one another; an orientation estimating unit configured to estimate orientations of the capsule endoscope at a plurality of points in a plurality of sub-regions obtained by dividing the region in a lattice form based on positional relationships between the points and the receiving antennas, and the received strength of the signals received by the receiving antennas; and a position determination unit configured to determine the position of the capsule endoscope in the subject based on the positions of the points and the orientations of the capsule endoscope, wherein the orientation estimating unit is configured to acquire a candidate region of a point at which a vector representing the orientation of the capsule endoscope passes based on a direction of the receiving antenna, a direction from the point to the receiving antenna, and the received strength at the receiving antenna, and is configured to determine a position where the candidate regions of the point at which the vector passes overlap with one another, the candidate regions being acquired respectively for the plurality of receiving antennas, and wherein the position determination unit is configured to calculate theoretical values of the received strength of the signals received by the plurality of receiving antennas based on the positions of the points and the orientations of the capsule endoscope in a case of assuming that the capsule endoscope exists at the points, as well as acquiring measured values of the received strength at the plurality of receiving antennas, and is configured to detect a point having a minimum error between the theoretical value and the measured value as the position of the capsule endoscope out of the plurality of points.