An illumination system includes a plurality of lighting fixtures, a plurality of slave devices, and an information communication terminal. Each of the plurality of slave devices includes: first wireless communication circuitry configured to receive, from each of the plurality of lighting fixtures, a signal including a MAC address of the lighting fixture, and to measure a received signal strength indication (RSSI) of the signal received; and a first controller that causes the first wireless communication circuitry to transmit the MAC address and RSSI information indicating the RSSI measured. The information communication terminal includes a second controller that makes associations between positions and MAC addresses of the plurality of lighting fixtures based on the RSSI information and position information stored in a storage.