To measure temperature of an optical waveguide with high accuracy, and reduce electric power consumption.

An optical waveguide device is disclosed that includes an optical waveguide formed on a substrate, a heater which is laminated on the optical waveguide to heat it, and a temperature sensor which is laminated on the heater through an insulation film and which detects the temperature. The optical waveguide has an optical waveguide core and a clad covering the circumference of the optical waveguide core. On both sides of the clad, a groove is provided along the longitudinal direction of the waveguide core. The temperature sensor is laminated on the heater, so that an amount of heat given to the optical waveguide can be measured with high accuracy. In addition, the temperature sensor is placed on the heater, thereby the width of the optical waveguide can be made smaller, resulting in the reduction of the power consumption of the heater.