Abstract
It is important to prevent project failures by Risk Management and Lessons learned. However, there is a tendency to exaggerate the benefit of them. In the Study of Failure, it is insisted on Failure prevention by Cause analysis. Although that is a plausible thinking, we must pay attention to cases which knowledge gained after the event is mixed in such kind of knowledge distributed. In this paper, the author consider that Ethics view-point is available for suggestion to provide solution to these problems and try to discuss its benefit.