A microvibration feature quantity apparatus includes a beat signal receiver receiving a beat signal output from a Doppler sensor, which radiates a radiation wave at a predetermined frequency to a body to be observed and senses part of the radiation wave reflected by the body to output the beat signal at a frequency corresponding to a difference in frequency between the radiation wave and the reflected part of the wave, a frequency converter transforming the received beat signal into a frequency-domain signal, and a beat signal feature quantity calculator using the frequency-domain signal to derive a beat signal feature quantity exhibiting an abrupt change with respect to time of a vibration velocity of the microvibration, thereby accurately calculating a feature quantity of the microvibration raised in the body.
