AbstractFrom the measurement of a reflected voltage waveform from a biological body for a step‐like voltage waveform, the frequency characteristics of the complex relative permittivity are studied and the following results are obtained: (1) if the blood flow and sweating are normal, the value of tanδ in the mouth is 4 ‐ 6 at about 10 MHz because electrochemical materials are contained in a large quantity. At frequencies below 100 MHz, the value is larger than those at the face, upper arms, legs and torso and its decrease with respect to frequency is larger. The back of the foot and the thenar have relative permittivities and tanδ's lower than other parts and hence are suitable for measurement of emotion functions; (2) in a physical exercise which causes a change in blood condition without sweating, the value of tanδ in the moving part increases as the number of motions is increased. In addition, the frequency characteristics below 1 GHz change significantly. The value of tanδ in the portion not related to the motion increases even after termination of the motion. Hence, the effect of the exercise can be evaluated from tanδ; and (3) as sweating progresses, the reduction of the permittivity becomes significant at frequencies below 100 MHz while the increase of tanδ is significant below 1 GHz. Hence, the sweating activity can be evaluated from the complex relative permittivity.