An inter-record alteration detection code verification unit 36 calculates an inter-record alteration detection code by merging a record alteration detection code stored in a record to read from a database 34 and a record alteration detection code in the immediately previous record so as to generate a code and applying a predetermined hash operation to the generated code. The verification unit verifies whether the calculated inter-record alteration code coincides with the inter-record alteration detection code stored in the record to read. If they coincide with each other, data is determined to be not altered.