The policy of “preventive maintenance of infrastructures” is to exercise preventive works in early stages of deterioration before infrastructure facilities cease to be functional. It aims at reduction and leveling of total cost of maintenance over life cycle of facilities. As of now, preventive maintenance is successfully assumed and put into practice by administrators of Sabo‐related facilities. Priorities for improving its effectiveness are;1) enhanced precision of deterioration projection of each facility given that efficiency of preventive works depends on the shape of deterioration curve. 2) disposition of engineers qualified for on‐site inspection and evaluation of deterioration. Provision of database of results of inspection, evaluation and preventive works executed by administrators is expected to contribute to both.