A method of measuring of an electrical bio-impedance, the method being characterized in that a symmetrical bipolar pulse-form periodical excitation signal (electrical current or voltage) is applied to the input (11) of the bio-object (1), a corresponding reaction of the bio-object to the mentioned excitation signal is measured from the output (12), which is connected to the input (201) of the synchronous detector (200). A symmetrical bipolar pulse-form periodical signal is also applied to the reference input (202) of the synchronous detector (200), whereby both pulse-form signals are shortened by the predetermined time interval in each half period of the signal, said time intervals being different for the excitation and reference signals. The proposed method ensures an increased accuracy of the impedance analysis by decreasing the influence of the higher harmonics in the spectra of the excitation and reference signals of the synchronous detectors to the measurement result. The use of the rectangular signals ensures that the device for implementing of the proposed method has a simple design and low power consumption.