An optical waveguide is provided to minimize a problem due to the weakness of adhesive force of a reflective mirror by applying a matching layer for matching a refractive index between a sidewall of a waveguide medium groove and a reflective block. An optical waveguide(100) includes a waveguide medium(110), a reflective block(120), and a refractive index matching layer(130). The waveguide medium has at least one groove(113). The waveguide medium is formed so that a sidewall(111a) exposed by the groove is inclined with respect to a traveling path of light. The reflective block has a reflective mirror(121) facing the inclined sidewall of the groove and is inserted into the groove so that the reflective mirror faces the sidewall of the groove. The refractive index matching layer is applied between the sidewall of the groove and the reflective mirror.
