The electrically equivalent circuit of a transfer belt is expressed as a parallel circuit of resistance and capacitance. Using this equivalent circuit, we determined the dependence of relaxation time on voltage from the attenuation characteristics. In addition, we proposed and evaluated a method of measuring a dielectric constant under a high voltage to obtain a dielectric constant. From this result, we demonstrated that the dependence of relaxation time on voltage is caused by volume resistivity and determined the dependence of volume resistivity on voltage. Furthermore, to check whether the obtained dielectric constant and volume resistivity reflects the behavior in the transfer phenomenon, we made both theoretical calculations and experiments based on the step response characteristic and verified that the results are in good agreement.