To prevent missing child/leaving of a person to be protected without complicating configurations related to communication.

A guardian management system 1 is provided with: a mobile station tag T1 movable in a prescribed mobile region with a guardian P1; mobile station tags T2 and T3 movable with persons P2 and P3 to be protected; and fixed station readers R1 to R4 equipped with a reader antenna 12. The location of the mobile station tag T is detected on the basis of radio signals transmitted from the mobile station tags T1 to T3, and received by the fixed station readers R1 to R4. Distance between the mobile station tag T1 and the mobile station tags T2 and T3 are detected on the basis of the location detection result. Whether or not the detected distance is equal to more than prescribed warning distances is decided. When the decision is satisfied, a corresponding warning instruction signal is generated and output. The mobile station tag T1 is provided with a display part DP for displaying corresponding warning, and for displaying the location of the mobile station tag T on the map according to the warning instruction signal.