The present invention relates to an impedance measuring device obtaining impedance of portions of an object corresponding to two sensing electrodes by detecting, through the two sensing electrodes, an electrical variation shown on the object as an electrical signal is applied. A detector amplifying each of signals detected through the two sensing electrodes and then differential-operating the amplified signals to generate a signal for obtaining impedance is subjected to a calibration process for adjusting the gain of the amplifiers to reduce in-phase noise added due to an imbalance between the sensing electrodes.
