The present invention relates to providing the manufacturing method for a magnetic disk drive that includes the process steps of detecting and processing in a simplified way the defective sectors causing a reading error at low operating environmental temperatures. In one example, defective sectors are detected by read/write testing at high operating environmental temperatures from, for example, 40° C. to 65° C. Reading the data written on the defective sectors makes it obvious that the gain in a high-frequency band is reduced. After test data has been written onto each sector, the filtering coefficient of an FIR element that is set for a data-reading system is changed from the optimum value. The frequency gain is thus reduced. Next, the test data is read and the sectors that have caused a reading error are registered as defectives.