PROBLEM TO BE SOLVED: To provide a mechanism capable of managing attribute information on an existing underwater structure which is relocated from a different place to be used in addition to attribute information on a new underwater structure.SOLUTION: A management device 20 acquires attribute information including at least identification information on a block B, distinction information representing whether the block B is a relocated block B relocated from a different place to be used or a new block B not relocated from a different plate, position-before-relocation information representing an installation position before relocation when the block B is the relocated block B, and installation position information representing the installation position of the block B, and stores the acquired attribute information in a database. The management device 20 outputs the attribute information stored in the database at a request from a user.
