A database restructuring support system that enables a user to flexibly design the structure of a database after a restructure.A storage cost estimate unit 112 calculates storage cost before and after restructure by using catalog information included in a database 122. In the case of calculating the storage cost of the restructure, tuples of a new schema is calculated and the storage cost is calculated by using the tuples. The access cost estimate unit 113 uses the catalog information and the log DB 121 included in the database 122 to calculate each access cost before and after restructure. In the case of calculating the access cost after restructure, the number of types of values of an attribute in the new schema is calculated to calculate the access cost by using the number of types. The integrated cost estimate unit 111 calculates the integrated cost by integrating the access cost and the storage cost.