A body temperature measuring apparatus is comprised of a terminal apparatus and a body temperature detection unit. The body temperature detection unit comprises a power supply unit for converting a voice output signal from the terminal apparatus into electricity, a detection unit for detecting infrared energy from the user's skin surface as a temperature detection signal, and a conversion unit for converting the temperature detection signal into a voice input signal. The terminal apparatus comprises a oscillation means for oscillating a voice output signal to the body temperature detection unit, and a measurement means for estimating the user's body temperature corresponding to the surface temperature of which the variation is small based on the voice input signal received form the body temperature detection unit, an emissivity of the user's skin surface, and the temporal variation of the surface temperature calculated within a predetermined measurement time.
