To provide a three-dimensional position determination system for measuring a three-dimensional position of a mobile object or the like, and guiding the mobile object or the like to a specific position; and a three-dimensional position determination method used in such a three-dimensional position determination system.

This three-dimensional position determination system 10 includes four sound wave transmitters 12, 14, 16 and 18 attached to a ceiling or the like, Ultrasonic waves transmitted from the sound wave transmitters 12-18 are detected by a sound wave sensor 20. The ultrasonic waves are transmitted from the sound wave transmitters 12-18 at certain time intervals, and the three-dimensional position of the sound wave sensor 20 is calculated from the detection interval when the ultrasonic waves are detected by the sound wave sensor 20. On the contrary, the sound wave sensor 20 is guided to a specific position by controlling transmission timing of the ultrasonic waves in the sound wave transmitters 12-18 by calculating back the arrival time of the ultrasonic waves at the sound wave sensor 20.