This paper described about heating properties of RF (Radio Frequency) heating applicator for hyperthermia treatments. Hyperthermia is based on clinical fact that malignant tissue is weaker than normal tissue under the temperature range of 42 to 43 oC. In the clinic, needle applicator is used to heat deep seated tumor. The advantages of this heating system is local and direct heating is possible. On the other hand, it has some disadvantage, namely, invasive heating method and small heated area. Another major heating device is RF capacitive-type heating applicator. This applicator is consisted from two discoid electrodes. Patient body is sandwiched between these electrodes and is heated by RF electric energy. The advantage of this heating device is non-invasive method and controllable of the hotspot location inside patient body by changing diameter of electrode. However it is not easy to heat deep region of patient body without undesirable hotspot around fat layer. In this paper, first we described about basic heating properties of needle-electrode applicator by using Finite Element Method (FEM). Second, we described about heating properties of RF capacitive-type heating applicator by changing size of two electrodes.