The optical waveguide device includes a first optical coupler which branches input light and outputs first signal light and second signal light, an optical phase shifter including a first and a second optical waveguides of optical path lengths different from each other and giving a phase difference between the first signal light and the second signal light, and the second optical coupler coupling the first signal light outputted from the first optical waveguide and the second signal light outputted from the second optical waveguide. The first optical waveguide and the second optical waveguide have the same waveguide width and have optical waveguides bent with substantially the same radius of curvature.