This study develops the decision-making model, which made the norm the risk aiming at extending the examination from a viewpoint of the conventional disaster prevention to structure management for a slope among road structures. Specifically in consideration of the performance deterioration about the stability of a slope, the life cycle cost based on the risk assessment result at the time of assuming rain as a natural hazard is calculated. Also, its attention is paid to the performance deterioration resulting from the groundwater counter measurement system by this study. It expresses using a multi-tank model about the groundwater behavior used as the performance deterioration. Furthermore, while making reference about the influence affect the calculation result of the life cycle cost paying attention to a social discount rate, the appraisal method which results in planning of the optimal maintenance repair plan based on risk assessment is proposed.