An estimating unit estimates, when there is a request for data in a system in which an error checking unit of data is formed with a plurality of memories each of which is a dual memory having an independent address line, whether an error has occurred on the address line based on a result of an error checking for data related to the request. A control unit generates, when it is estimated that an error has occurred on the address line, error data of the data related to the request, and controls the memory in such a manner that one line of the dual memory is disabled by switching the data related to the request to generated error data.