To improve a detection accuracy and manufacture efficiency of an optical device such as an optical pressure sensor.

The optical pressure sensor 1 is equipped with: an optical waveguide 3 formed on one substrate surface of a silicon substrate 2; a pressure receiving chamber 5 formed on the other substrate surface; and a diaphragm 6 formed on a bottom part of the pressure receiving chamber 5. Namely, the optical waveguide 3, the pressure receiving chamber 5 and the diaphragm 6 are integrally formed on one silicon substrate. Hereby, when the diaphragm 6 is displaced in a vertical direction or the like by a pressure of fluid flowing into the pressure receiving chamber 5, the displacement is transferred accurately and directly to a Bragg grating 4. The pressure of the fluid is thereby detected highly accurately with excellent responsiveness.