We are studying about the evaluation method of thermal fatigue characteristics for the epoxy resin for mold used as the mechanical protection and the electric insulation material of electrical and electric equipment. Since the strength of an epoxy resin is strongly dependent on temperature, when obtaining repetition thermal stress with starting and stopping of product, it becomes reverse phase type thermal fatigue problem. Then, paying attention to strong temperature dependency, the technique of predicting thermal-fatigue characteristics from the machine fatigue characteristics under constant temperature is proposed, and the validity based on a metal-fatigue mechanism is verified. By the result of research, the rational choice of a rational design and an epoxy resin to a thermal fatigue is made possible.