A database restructuring apparatus which is capable of migrating a database without depending on a method of managing the database and without interrupting practical online services. Copying section copies data from a current database to a switching destination database. When data update access to the current database by current database access section occurs during copy processing by the copying section, data updating section determines whether or not data to be accessed has been copied. If the data has not been copied yet, the data updating section performs data update processing on the current database, whereas if the data has already been copied, the data updating section performs data update processing on both the current database and the switching destination database. After completion of the copy processing, switching section switches the distribution destination of an online electronic message to switching destination database access section.