A thermal head manufacturing method comprises a concave portion forming step of forming a concave portion on one surface of a supporting substrate, a bonding step of bonding a thin plate glass to the one surface of the supporting substrate where the concave portion has been formed in a manner that hermetically seals the concave portion and forms a hollow portion, a heating step of heating the supporting substrate and the thin plate glass which have been bonded together in the bonding step to thereby soften the thin plate glass and expand gas trapped inside the hollow portion, and a heating resistor forming step of forming a heating resistor on the thin plate glass so as to be opposed to the hollow portion. During the heating step, the thin glass plate undergoes plastic deformation, due to expansion of the gas inside the hollow portion, and rises toward an opposite side from the hollow portion, and a leveling step is carried out to level the outer surface of the plastically deformed thin glass plate.