Abstract: The object of the present invention is to provide an electrode device for high frequency thermotherapy, including a main casing, an electrode needle, a first engaging part, and a guide unit coupled to the engaging part to be longitudinally moved relative to the electrode needle. The guide unit has a guide tube to receive therein the electrode needle to expose a tip of the electrode needle to the outside of an end of the guide tube. Thus, the exposed length of the tip of the electrode needle is varied according to a position that the guide unit is coupled to the engaging part. The electrode device may further include a three-way valve -provided between the main casing and the guide unit to supply a liquid medicine or water t a desired part of a patient body.