A slew-rate control device controls a slew rate of a control signal based on which data reading or data writing is performed with respect to a storage medium. A retry executing unit changes, when an error occurs during the data reading or the data writing, the slew rate of the control signal, and executes a retry of the data reading or the data writing. A slew-rate setting unit sets, as the slew rate of the control signal, a slew rate with which the retry is successfully executed.