PURPOSE: To attain efficient design of the titled element by using an optical vibration sensor to detect the surface displacement of a surface acoustic wave generated from an interdigital electrode for generating a surface acoustic wave whose frequency characteristic is known, by means of an optical vibration sensor with excellent spatial resolution.

CONSTITUTION: A reference sinusoidal wave signal generated in a reference signal generating circuit 2 is amplified and sent to the interdigital electrode 1 for generating a surface acoustic wave whose frequency characteristic is known beforehand. The surface acoustic wave generated is propagated toward the other end of the component along the surface of the surface acoustic wave element 4. The surface vibrating displacement of the surface acoustic wave is detected by an optical vibration sensor 5. A detection circuit 9 measures the signal amplitude and a phase difference between a reference sinusoidal wave signal from a reference signal generating circuit 2 and a vibrating displacement signal and sends the result of a central arithmetic processing/ control section 10. The surface acoustic wave element 4 is fixed to a 2-axis stage 11, and moved accurately in parallel with the optical system by the central arithmetic processing/control section 10. Thus, the frequency characteristic of the electrode of an optional shape is simulated without the need for actual formation.