In hyperthermia, it is necessary to heat the tumor over 42.5°C to get anti-tumor effects. However, it is very difficult to heat the target to an ideal temperature, because subcutaneous fat might also be heated simultaneously. Various activities for the improvement of heating more efficiently, such as applying medical jelly, pasting of the tape, the gripping method and reposition of a patient were performed in many therapeutic facilities. In this research, we focused on the other properties to improve the heating efficiency, such as utilization of overlay bolus and the difference of the electrode pad thickness. We tried experimental approach about the difference in heating efficiency according to the two factors.