A position detecting apparatus of a capsule endoscope includes a receiving antenna unit that receives a wireless signal transmitted together with an image data signal from the capsule endoscope in a subject via a plurality of receiving antennas, a correlation level calculating unit that calculates a correlation level between the image received by the receiving antennas and an image received immediately before the image was received, a determining unit that determines whether a position and/or direction of the capsule endoscope is changed, based on the correlation level calculated by the correlation level calculating unit, and an estimating unit that estimates the position and/or direction with respect to the position of the capsule endoscope at the time the image was captured if the determining unit determines that the position and/or direction of the capsule endoscope is changed.
