An impedance measurement device for outputting an AC current of a prescribed frequency to the positive-electrode terminal and the negative-electrode terminal of a layered battery, and detecting the AC potential difference between the positive-electrode terminal and an intermediate-point terminal, and the AC potential difference between the negative-electrode terminal and the intermediate-point terminal. The impedance measurement device adjusts the amplitude of the AC current in a manner such that the AC potential difference between the positive-electrode terminal and the intermediate-point terminal and the AC potential difference between the negative-electrode terminal and the intermediate-point terminal are identical, and calculates impedance on the basis of the adjusted AC current and the AC potential difference. The impedance measurement device corrects the phase difference of the AC current outputted to the positive-electrode terminal and the negative-electrode terminal, on the basis of the phase difference between the AC potential produced in the positive-electrode terminal and the AC potential produced in the negative-electrode terminal.