A heat therapy for thermally treating a target tissue within a living body by using a treating apparatus including a treating device with a magnetic part is provided. The magnetic part is heated to a first temperature by a high frequency electromagnetic field with a heating rate ranging from 1 to 5° C./sec, wherein the magnetic part is contacted the target tissue. Temperature controlling steps are performed to the magnetic part having the first temperature, and therefore the magnetic part has a final temperature higher than the first temperature, and a treatment is performed to the target tissue under the final temperature. Each of the temperature controlling steps is a heating step, a cooling step or a temperature conservation step, and the magnetic part is heated or cooled by the high frequency electromagnetic field with a heating rate or a cooling rate ranging from 1 to 5° C./sec.
