The purpose of this invention is to provide a position detection system with which it is possible to reliably detect the position of a mobile unit indoors or outdoors, regardless of the state of the outdoor environment. In order to achieve this purpose, when the position of the mobile unit is being identified by the beacon positioning system 2, the system switching unit assigns the beacon positioning system 2 priority, even if a satellite positioning system 1 is correctly identifying the position of the mobile unit; in a state in which the position of the mobile unit is not identified by the beacon positioning system 2, if the satellite positioning system 1 accurately identifies the position of the mobile unit, the system switching unit 3 switches from the beacon positioning system 2 to the satellite positioning system 1; and in a state in which the position of the mobile unit is not being accurately identified by the satellite positioning system 1, if the beacon positioning system 2 identifies the position of the mobile unit, the system switching unit 3 switches from the satellite positioning system 1 to the beacon positioning system 2.