Optical waveguide device 101 has waveguide 103 strip-shaped in the depth direction of the drawing and protruding from peripheral portion 102. A core (not illustrated) is disposed inside waveguide 103. Wall 106 to be cut is integrated with waveguide 103 to form one core layer. No unevenness occurs in a cutting line of wall 106 indicated with broken line 105. Accordingly, high-precision cutting is enabled by cutting wall 106 along the cutting line.