A data management device is communicably connected to a first database and a second database in a different structure from the first database. The second database is converted to the structure of the first database, and is stored as a conversion table based on first data schema information defining the structure of the first database and second data schema information defining the structure of the second database. For which database a query that is received from the outside and described corresponding to the structure of the first database is a query is determined with reference to the conversion table. When the query is determined to be a query for the second database, the query is converted and is introduced into the second database, and a query result in response to the query is converted into a format corresponding to the structure of the first database and output.