To obtain a modulator for polarization plane of light by embedding an optical fiber a single bond substrate having a large electromechanical coupling coefficient, also forming an IDT electrode and exciting surface wave.

A linear groove is formed a little to the left side from the center of a piezoelectric substrate 1 perpendicularly to a base. The optical fiber 2 is embedded in the groove and the IDT electrode 3 is formed a little to the right side from the center of the principal plane of the substrate 1. Then, a presser plate 5 covering over the optical fiber 2, the optical fiber 2 and the substrate 1 are fixed with an adhesive 6.