The general evaluation method of various kind of safety strategies for welfare and human-care robots is first proposed in the world. The impact force and impact stress are chosen as safety evaluation values to quantify safety. The dangerous index and safety index are defined to make quantitative evaluation of the effectiveness for each safety strategy. Moreover, this method enables us to know the contribution of each safety strategy to the overall safety performance of welfare robot. As a result, design optimization of the safety robot is discussed successfully.