Provided is an optical waveguide device capable of reducing stress that occurs inside an optical waveguide substrate due to a difference in a coefficient of thermal expansion. The optical waveguide device (10) includes an optical waveguide substrate (11) having a thickness of 30 μm or less, and a liquid crystal polymer substrate (12) which holds the optical waveguide substrate (11) and has permittivity lower than that of the optical waveguide substrate (11). The optical waveguide substrate (11) and the liquid crystal polymer substrate (12) are bonded to each other by an adhesive layer (14). Coefficients of thermal expansion of the optical waveguide substrate (11) and the liquid crystal polymer substrate (12) have anisotropy in each substrate plane, and a relative direction between the optical waveguide substrate (11) and the liquid crystal polymer substrate (12) is adjusted in such a manner that anisotropic axial directions of the optical waveguide substrate (11) and anisotropic axial directions the liquid crystal polymer substrate (12) are aligned.