A high yield in a manufacture of an HDD having a high recording density and using a patterned medium by a trench-like or a dot-like pattern is realized. In this HDD manufacturing method, a magnetic field size (writing and reading) of a head in a head manufacturing process is measured in a head unit inspection process. According to the result of the measurement, the head is classified into a plurality of groups in a head classifying process. In a patterned medium manufacturing process, a plurality of types of the patterned media which are designed so as to correspond to the classified head groups are manufactured. In an HDD assembly process, the HDD is manufactured by combining the plurality of head groups and the plurality of patterned media following a predetermined rule.