PROBLEM TO BE SOLVED: To provide a body temperature monitoring system for an in-flight passenger capable of accurately detecting a feverish patient with suspected infection of a new type virus, etc. who is determined to be in need of isolation, prior to entry into the country.SOLUTION: A temperature of an in-flight passenger seated on a seat 10 is measured by a small-sized infrared camera attached to the back face of a front seat. A feverish patient is detected from measured temperature data, and displayed on a seat monitor 40 installed in a flight attendant station together with a position of the seat so as to attract attention of flight attendants. A temperature history, an entry-exit history, etc. of the passenger which are useful in determining whether or not the feverish patient needs to be isolated are displayed on the seat monitor 40.SELECTED DRAWING: Figure 1