Abstract: A method of applying heat to living tissue mainly uses a device for performing heat treatment on at least a portion of the living tissue in high-low-high temperature steps. In high temperature step, the temperature of the at least a portion of the living tissue is heated and kept between 39-46° C., and the heating period is no longer than 30 minutes. In low temperature step, the at least a portion of the living tissue is cooled, and the low temperature period should not be greater than a natural cooling time interval. In addition, the low temperature period must also be shorter than the heating period. Thus, the present invention allows the abnormal cells to be selectively restored or apoptotic without damaging the normal cells.