Abstract
A software development is complicated and the situation grasp of the development project becomes difficult. Therefore, it is difficult to identify the root cause of the problem and to work-out of the improvement policy. In this paper, we discuss the way of analyzing complicatedly intertwining causality based on the data about QCD (the quality, the cost, the appointed date of delivery) which was measured from the project. Specifically, we have reviewed the way of utilizing the information visualized by data mining for the thinking process of the cause and effect reasoning. We introduce the case to have applied this way to the problem analysis of the software development project and consider the usability of the technique.