An optical module and its manufacturing method are provided which are capable of forming an optical waveguide by making the most of characteristics of a material having small optical transmission loss and excellent machinability or processibility. The FexSi2 has a symmetrical monoclinic crystalline structure belonging to the P21c space group and is synthesized at the surface or in the interior of the crystalline silicon. The second member can include pocket thread openings for attaching a pocket to the head.