There are provided a method of manufacturing a thermal head having a hollow portion at a position opposing a heating resistor, the manufacturing method assuring a sufficient strength to an upper plate substrate of the thermal head. The manufacturing method includes: processing a top surface of the upper plate substrate bonded to a support substrate to thin the upper plate substrate to a thickness T; wherein the processing comprises processing the top surface of the upper plate substrate so that a roughness Ra of the top surface of the upper plate substrate satisfies the following expression:: Ra≦loge(T2)/(3×106)+6.5×10−6.