To solve a problem in monitoring the remaining life of an electronic apparatus that the life is commonly estimated by monitoring the load acting on the apparatus such as the temperature change history, but the influence of loads which are not monitored is not considered and the predicted life may be widely different from the actual life due to these loads.

By establishing a dummy joint part which breaks down earlier than a target joint part, the life of which is to be estimated, the life of the dummy joint part is estimated from the measured load. By recording the load history until the dummy joint part actually breaks down, the life of the target joint part, the life of which is to be estimated, is calibrated, if the life estimated from the load history is widely different from the actual life. The calibration is performed by subtracting the value based on the influence of the loads, which are not measured, from the life obtained from the measured load.