A position detection system according to an embodiment of the present invention includes a plurality of fixed stations 20; and a sensor unit 10 including an inertial sensor that detects movement history of a mobile body 51 and a distance sensor that detects separation distances between the mobile body 51 and the fixed stations 20. A position of the mobile body 51 is determined by detecting a first arrival position P1 obtained based on the movement history, a second arrival position P2 obtained based on the separation distances, and a relative distance L1 between the first arrival position P1 and the second arrival position P2, and by comparing a range value R1 obtained based on the movement history with the relative distance L1. The range value R1 is changed based on the movement history.