To provide a moisture meter which can detect a heat-illness risk-index earlier and which is effective to assist a subject carry out a proper moisture adjustment includes: a moisture measurement unit held by an armpit of a subject and which measures the amount of moisture of the subject through contact with a skin surface of the armpit, a sensor unit which measures the temperature and humidity of the environment of the subject, and a processing unit which obtains the amount of moisture of the subject from the moisture measurement unit, which sets a Wet-Bulb Globe temperature (WBGT) value from the relationship between the temperature and humidity from the sensor unit and which obtains the heat-illness risk-index by referring to a relation table between the amount of moisture of the subject and the Wet-Bulb Globe temperature value.
