Recently, a hazard analysis technique STAMP/STPA has been widely accepted since it is recognized as being suitable for software-intensive systems. Using STAMP/STPA, we can find hazardous scenarios of the target system that cannot be obtained by other traditional hazard analysis methods and those scenarios can be used for validation testing. However, generally the number of obtained scenarios can be huge and the validation testing involves a considerable cost. In this study, we propose a method to prioritize hazardous scenarios identified by STAMP/STPA with the help of a statistical model-checking technique. We give a procedure for systematically transforming the model defined by STAMP/STPA to a formal model for a statistical model-checking tool. We also show the usefulness of the proposed method using an example of train gate control system.