A plurality of electrode pairs, each of which is constituted by two electrodes of the plurality of biomedical electrodes are set and at least one of an electrical impedance value between two electrodes forming a pair and a resistance value between the two electrodes, for each of the electrode pairs is measured. An attachment state of each of the electrode pairs is judged by comparing the impedance value or the resistance value, with a predetermined range of numeric values. An electrode in an inappropriate attachment state is identified from the plurality of electrode pairs based on the judged attachment state o each of the plurality of electrode pairs.