Abstract
Risk has various concepts and various knowledge is required of risk management. When that generates various problems, such as risk communication, it becomes difficult to carry out risk management effectively. The risk management knowledge system RiMBOK for having common concepts about risk as means to solve this problem was built. This paper introduces RiMBOK which is one of the activity results of PMI Tokyo chapter's Risk management study group, and considers problems based on experience which built RiMBOK.