PURPOSE: To measure easily and precisely the conductance of an epidermal horny layer by changing a flat tuning curve according to the conductance of the epidermal horny layer via a quartz oscillator, a buffer amplfier and two sets of tuners and detecting the same.

CONSTITUTION: The high frequency output from a quartz oscillator 1 is made into the output of the voltage in which the vltage e2 in the flat tuning curve having a single peak response is equal to the voltage of the high frequency output from a buffer amplifier 2 by a tuner 3 provided with coils 305, 306, coupled coarsely by a critical coupling via the amplifier 2. The output is made into the tuning curve output changing in proportion to the conductance GX corresponding to moisture irrespectively of the capacity Cx of an epidermal horny layer 5 by a tuner 4 provided with a coil 401 having adjusted tap positions. The output from the amplifier 2 and the output from the tuner 4 are processed respectively with detectors 6, 7 and are added to a differential amplifier, then the conductance of the epidermal horny layer having a high correlation with the moisture contained therein is measured easily and precisely.