An optical wave guide device is manufactured by bonding an optical wave guide to an optical modulator through an upper cladding layer. The optical wave guide includes a glass substrate, a lower cladding layer and cores, and the optical modulator includes elements (heaters), which are disposed on the lower surface of a glass substrate, for modulating the light propagating in the cores, and electrodes and wire bond pads which are disposed on the front surface thereof. The elements are connected to the electrodes via through-holes. With this arrangement, there can be provided an optical waveguide device, in which cores are not degraded in manufacturing processes and elements for modulating the light propagating in the cores are unlikely to be exfoliated.