PURPOSE: To inexpensively provide a temperature-monitoring device for surely preventing an electronic equipment from malfunctioning or failing by heating.

CONSTITUTION: A temperature monitoring device is provided with a first temperature detector 1 for detecting the temperature at the intake port side of an enclosure 20 of an electronic equipment where air is blown in a blast path from an intake port to an exhaust port by a blower, a second temperature detector 2 for detecting the temperature of the exhaust port side of the enclosure 20, a third temperature detector 3 for detecting the internal temperature of the enclosure 20, and a means for monitoring the temperature change inside the enclosure 20 and the temperature inside the enclosure 20 based on the difference of temperatures detected by the first and the second temperature detectors 1 and 2, and the detection result of the third temperature detector 3.