PURPOSE: To enable highly accurate evaluation of sweating condition of a person to be measured by arranging a sensor head section contacting a skin surface of a human body as exposure electrode to measure an electric resistance of the skin surface at a specified measuring frequency.

CONSTITUTION: With a measuring frequency in the range of 10Hz to 10MHz, sweating condition can be evaluated accurately by measuring a complex impedance of a skin surface. A band is used to fix a perspiration sensor on a body surface of a wrist so that a first exposure electrode 2 contacts a body surface. Here, a second exposure electrode 5 is provided at a position contacting none of the skin surface. As the second exposure electrode 5 does not contact the human body, it indicates a large impedance change only for external conditions, for example, wetting by water. Thus, the first and second exposure electrodes 2 and 5 indicate the same impedance, for example, in wetting by a rainwater to allow discrimination between wetting by water and sweating condition thereby achieving an accurate evaluation of the sweating condition in ranks.