There is provided with a data analysis method, including: providing a database storing for each of devices an example that includes inspection time, the degradation level, operation characteristics, and replacement information; providing a evaluation maintenance strategy including an evaluative inspection time, an evaluation time and evaluative replacement condition; providing a prediction model for predicting the degradation level of a device from operation characteristics thereof; estimating by using the database an estimated number of devices that have already been replaced before the evaluation time, evaluating the degradation level at the evaluative inspection time of each of as many devices as estimated number and devices subjected to inspection of same periodic inspection time as the evaluation time; and evaluating the degradation level at the evaluation time of devices whose degradation level at the evaluation inspection time does not satisfy the replacement condition.