A skin impedance measuring device and method includes: an electrode system having at least two electrodes placed on the skin; an adjustable voltage output unit to generate forward and reverse voltages on the electrodes; a skin impedance measurement unit to measure electrical signals from the electrodes; a central processing unit and a computing memory for calculating forward and reverse skin impedances, determining whether the measurement results are abnormal, and correcting abnormal results by delivering additional DC or AC voltages of adjustable magnitudes and frequencies based on impedances; and a display unit.