Abstract: The present invention relates to a high speed accurate temperature measuring device especially useful for measuring human body temperature, comprising (a) an elongated temperature probe, (b) a first temperature sensor located beneath the surface of the probe, (c) at least one second temperature sensor located within the probe and parallel to the first sensor, (d) a thermal insulation member located between the first sensor and the second sensor (or sensors), (e) a data processing unit connected to the first and second temperature sensors calculating the body temperature according to heat flux measured between the body and the first sensor and between the first sensor and the second sensor (or sensors), and (f) a data display connected to the data processing unit.