The objective of the present device is to capture a temperature change within a living body without delay. A living body internal temperature measuring device 1 is provided with an ultrasonic wave radiating unit 2 for radiating ultrasonic waves toward a living body 10, an ultrasonic wave detecting unit 3 for receiving ultrasonic waves reflected by the living body 10, and a computing unit 5 for calculating an amount of change in temperature within the living body 10. The computing unit 5 calculates a frequency of ultrasonic waves amplified within the living body 10 on the basis of information relating to the structure of the living body, acquires an amplitude spectrum of the ultrasonic waves received by the ultrasonic wave detecting unit 3 by subjecting the ultrasonic waves to frequency analysis, obtains, from the amplitude spectrum, a peak frequency closest to the frequency of the ultrasonic waves amplified within the living body 10, calculates an amount of change in frequency from two peak frequencies obtained by performing ultrasonic wave radiation twice, and calculates the amount of change in temperature within the living body 10 from the amount of change in frequency.L'objectif du présent dispositif est de capturer sans retard une variation de température dans un corps vivant. Un dispositif de mesure de la température interne d'un corps vivant (1) est pourvu d'une unité d'émission d'ondes ultrasonores (2) permettant d'émettre des ondes ultrasonores en direction d'un corps vivant (10), d'une unité de détection d'ondes ultrasonores (3) permettant de recevoir des ondes ultrasonores réfléchies par le corps vivant (10), et d'une unité de calcul (5) permettant de calculer l'ampleur de la variation de température dans le corps vivant (10). L'unité de calcul (5) calcule la fréquence des ondes ultrasonores amplifiées dans le corps vivant (10) sur la base d'informations relatives à la structure du corps vivant, acquiert un spectre d'amplitude des ondes ultrasonores reçues
