To prevent an object from going out without notice and without carrying a portable terminal in a system for making an aged person suffering from senile dementia carry a portable terminal to inform of wandering.

In a wonderer informing system for detecting and informing of action that a monitored object goes out from a prescribed area to the outside, the portable terminal is provided with a communication means for communicating with a monitor by a near distance radio signal and a vital sensor for monitoring object's vital information and constituted so as to receive a polling signal from the monitor by the communication means, transmit a response signal, and when vital information is not detected by the vital sensor, output abnormality report by the communication means. When a response signal is not received within prescribed time from the transmission of the polling signal, the monitor determines that the monitored object is out, and at the time of receiving an abnormality report, performs warning operation.