To provide a mobile body information system and mobile body exploring system wherein, with reduced power consumption, and wear of battery is less.

At a transmitter 11, transmission interval is normally set at an initial value, moving speed of an aged person 2 is above a set speed, transmission interval is shortened. Thus, power source supply to a transmission circuit is intermittent, and with a changeable transmission circuit, the information (position information, ID number information) about roaming person 2 is transmitted from the transmitter, by wireless telephone, to an explorer device 13, resulting in less battery wear.