While suppressing the calculation amount, to provide a position detecting device or the like capable of performing position detection of the capsule endoscope with higher accuracy than conventional. The information processing apparatus 6, based on each reception intensity of the plurality of receiving antennas receives signals, obtains a distance between the receiving antennas and the capsule endoscope, corresponding to each of the receiving antennas around the respective receiving antennas the distance between existence region acquisition unit 621 for acquiring a plurality of areas at least two spheres overlap among the sphere whose radius a, the positional relationship between each and each receive antenna of the plurality of points within the region, and each receive antenna receives based on the reception strength of the signal, the direction estimating unit 622 that estimates the orientation of the capsule endoscope at each point, based on the orientation of the position and the capsule endoscope of the above points, in the subject and a position determining unit 623 for determining the position of the capsule endoscope.計算量を抑えつつ、従来よりも高い精度でカプセル型内視鏡の位置検出を行うことができる位置検出装置等を提供する。情報処理装置6は、複数の受信アンテナが受信した信号の各受信強度をもとに、各受信アンテナとカプセル型内視鏡との距離を求め、各受信アンテナを中心として各受信アンテナに対応する距離を半径とする複数の球のうち少なくとも2つの球が重なり合う領域を取得する存在領域取得部621と、領域内の複数の点の各々と各受信アンテナとの位置関係、及び各受信アンテナが受信した信号の受信強度に基づいて、各点におけるカプセル型内視鏡の向きを推定する向き推定部622と、上記各点の位置とカプセル型内視鏡の向きとに基づいて、被検体内におけるカプセル型内視鏡の位置を決定する位置決定部623とを備える。
