To reduce an error due to stray capacitance or leakage currents of an electronic circuit positioned at the connection terminal of an object to be measured in an impedance measuring equipment and an admittance measuring equipment.

An AC signal voltage (Vi) is added to the positive phase input terminal of a differential amplifier (D1), and the AC signal voltage Vi is added to the supply power source of the differential amplifier D1 by a voltage duplicating means (M1). An impedance being an object to be measured is connected with an anti-phase input terminal, and currents running through this are converted into a voltage by the differential amplifier D1 and rectified, and applied to a DC signal for instructing the impedance and an admittance.