Abstract: An apparatus for diagnosing the functions of the internal organs and the autonomic nervous system of the living body in which a constant voltage is applied across two or more electrodes attached to the living body, a current flowing across the electrodes and changing from time to time is detected at high speed and recorded, and predetermined parameters are calculated from the recorded data is disclosed. The electrodes are sequentially or arbitrarily scanned by an electrode scanning means (2), and the constant voltage generated by a constant voltage generating means (3) is applied to the scanned electrodes. The instantaneous value of the current flowing across two electrodes is detected by a detecting means (4), and recorded as a digital value in a recording means (5).