To calculate an antenna position inside a building and to detect the location of a traveler by transmitting calling signals to the boarding pass of an unboarded traveler who checked in and detecting an antenna which receives response signals from the boarding pass.

When a boarding pass reader (BPR) 3 inspects the boarding pass 2 and counts a boarded person number, a boarding pass issuing device (BPP) 11 issues the boarding pass 2 of the traveler who checked in and outputs an issued number to a personal computer 9. The personal computer 9 displays the positions of the antennas inside the building, a boarding pass issued number and the boarded person number at a CRT 9a. In the case that the unboarded traveler who checked in is present from the displyed issued number and the boarded person number, a person in charge at an airport operates a transmission circuit 6 and transmits the calling signals to the boarding pass 2 of the unboarded traveler by using the plural antennas distributed and arranged in an airport building. An antenna detection circuit 8 detects the antenna which receives the response signals. The person in charge recognizes the position of the antenna by the display of the CRT 9a and easily finds the unboarded passenger present near it.