An optical waveguide device includes a lower cladding layer, a high refractive index region provided on the lower cladding layer, a pair of cores provided on the lower cladding layer on both sides of the high refractive index region, and an upper cladding layer provided on the high refractive index region and the pair of cores. One of the upper and lower cladding layers has a pair of band-shaped parts disposed between the high refractive index region and the pair of cores.