PURPOSE: To avoid cost-up and to improve by setting a frequency characteristic so as to make it lower than a required value in metallic thin film forming process and patterning process and adjusting it to be the required frequency characteristic before chip dividing process.

CONSTITUTION: The thickness of a interdigital electrode part 9 formed in patterning process is reduced by a wet etching method so that frequency adjusting process adjusting the frequency characteristic is added between patterning process and chip dividing process. That is, the thickness of the interdigital electrode part 9 formed on a piezoelectric body substrate 10 is reduced by the wet etching method in frequency adjusting process. That is, the mass of an input and output per unit area in the interdigital electrode part 9 is reduced so as to be adjusted. Miscible liquid where acetic acid and pure water are in the proportion of 1:14 as against phosphoric acid being 1 in proportion is used as etching liquid which is used in the wet etching method. Here, the respective electrode parts are removed and re-processing is executed from metallic thin film forming process again concerning a surface acoustic wave device out of an etching rate range so that processing man-hour after chip dividing process is reduced.