It is indispensable to have scientific estimates of the runoff sediment volume and the peak discharge of debris flow in streams when considering both active and passive measures against debris flows. The purpose of this study is to propose an estimation method for the design runoff sediment volume from debris flow and the peak discharge of debris flow by means of the probabilistic safety assessment based on about 450data on debris flow throughout Japan listed in a literature. As a result on statistical analysis, there were relatively strong correlations both between the runoff sediment volume and the drainage basin area and between the peak discharge and the drainage basin area, but on the other hand, there were no significant correlation between both of the runoff sediment volume and the peak discharge and both precipitation and geology. An estimation method for the design runoff sediment volume and the design peak discharge via the drainage basin area by the 95% or 99% prediction interval of the data obtained by using the past survey results was proposed.