Embodiments in accordance with the present invention relate to identifying an address of user data to be registered as a defective user data address in disk defect inspection. In an embodiment of the present invention, in the state where a write element is positioned to a target position to execute data write processing to execute normal data read processing, a write element executes data write processing. If a predefined error occurs during the data write processing, an address of user data for which the normal data write processing is executed is estimated using the error-causing servo data as a target. In addition, an address of the servo data used as the target during the normal data write processing for the estimated address of the user data is identified. If the identified address of the servo data and the address of the error-causing servo data match with each other, the estimated address of the user data is registered as a defective user data address.