A fatigue limit stress specification system includes: a vibration generator that repeatedly applies a load to an object to be measured; a temperature sensor that measures a change in temperature of the object to be measured; and an information processing device that measures a fatigue limit stress of the object to be measured on the basis of the change in temperature of the object to be measured that has been measured by the temperature sensor. The information processing device analyzes the change in temperature that has been measured by the temperature sensor, obtains a relation between a temperature amplitude of a fundamental frequency component of vibration for the object to be measured and a temperature amplitude of a second harmonic component of the vibration, performs fitting on the relation by using first approximate line (L1) and second approximate line (L2), first approximate line (L1) including a quadratic curve, second approximate line (L2) including a quadratic curve, and obtains the fatigue limit stress of the object to be measured based on an intersection of first approximate line (L1) and second approximate line (L2).
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