Abstract: A hard disk drive (HDD) stores a plurality of parameter data for determining a filter characteristic, which is necessary for the operation of a read/write circuit, to ROM in advance. At the time of driving HDD, a host computer designates parameter data in a predetermined order, and executes a verification processing with the operation of the read/write circuit for every parameter data. The host computer determines parameter data showing a minimum read error rate as a suitable value in accordance with the result of the verification processing. A CPU of HDD stores parameter data having the suitable value determined by the host computer to a nonvolatile read/write memory. CPU sets a parameter, which corresponds to parameter data stored in the read/write memory, in the read/write circuit.