With the development of national industry, the number of social infrastructure facilities is gradually increasing. In addition, as time goes by, the aging of facilities is progressing gradually. For this reason, the importance of maintenance to ensure the safety of facilities is continuously increasing. However, there is still a lack of effective ways to invest the maintenance budget of facilities. For this reason, advanced foreign countries are actively studying facilities asset management techniques. In this study, construction cost and depreciation method of existing major facilities(1,2 class) were applied to examine the asset size of existing facilities according to changes in the service life of facilities.