An optical waveguide device 1 includes a thin layer 3 and a ridge portion 5 loaded on the thin layer 3. The thin layer 3 is made of an optical material selected from the group consisting of lithium niobate, lithium tantalate, lithium niobate-lithium tantalate, yttrium aluminum garnet, yttrium vanadate, gadolinium vanadate, potassium gadolinium tungstate; and potassium yttrium tungstate. The ridge portion 5 is made of tantalum pentoxide and has a trapezoid shape viewed in a cross section perpendicular to a direction of propagation of light. The ridge portion is not peeled off from the thin layer in a tape peeling test.