To easily adjust the center frequency of an SAW(surface acoustic wave) filter by measuring the input/output characteristic including the frequency characteristic of an SAW device and repeating both etching and oxide forming steps until the desired input/output characteristic is obtained.

A piezoelectric substrate 50 is placed in a chamber 52 having a terminal 70 which can measure the input/output characteristic including the frequency characteristic of an SAW device. In an etching step, the surface of an interdigital electrode constructing the SAW device is shaped by a method such as the dry etching. In an oxide forming step, an oxide is formed on the surface of the interdigital electrode. In a repeating step, the input/output characteristic including the frequency characteristic of the SAW device is measured via the terminal 70. Then both etching and oxide forming steps are repeated until the desired input/output characteristic is obtained.