An optical waveguide device includes: a substrate having an electro-optic effect, an optical waveguide formed on the substrate, a light-receiving element disposed on the substrate and monitoring a light wave propagating through the optical waveguide or a light wave that is radiated from the optical waveguide; and a monitoring optical waveguide extending from the optical waveguide to the light-receiving element, in which the monitoring optical waveguide has a U-turn waveguide with respect to an output direction of the optical waveguide, and the light-receiving element is disposed at a part of the monitoring optical waveguide after the U-turn waveguide.