Abstract: Providing a probe for an electronic clinical thermometer, which can measure a surface temperature and a deep body temperature of a human body securely in short time, the probe includes a cylindrical housing, a bottomed metal pipe fitted into a top end of the cylindrical housing, and a substrate having two thin-film heat-sensitive elements arranged perpendicularly on an inner wall of the bottomed metal pipe so as to fix one side edge of the substrate tightly on the inner wall. By measuring heat flux between the two thin-film heat-sensitive elements, the surface and the deep body temperatures of the human body can be predicted by applying the measured values into a heat conduction equation without waiting the sensor to reach in heat balance.