In a method for writing data having been subjected to transaction processing in a synchronization source database to data in a synchronization destination database, a synchronization processing management unit of the synchronization destination database requests, as synchronization target data, first data that is a part of the data having been subjected to the transaction processing from the synchronization source database, receives at least the first data from the synchronization source database, performs first synchronization processing on the first data in a cache memory, and performs second synchronization processing on second data, in the synchronization destination database, which has been processed in a same transaction as a transaction in which the first data has been processed in the synchronization source database.