An optical device is provided to prevent a dicing blade form being clogged when a wafer is cut by means thereof. Further, an optical device is provided to the present invention can prevent unnecessary expansion of a resin used in the optical device. The present invention relates an optical device having a substrate and an optical waveguide layer laminated thereon. The optical waveguide layer has a first lateral surface connected to an optical fiber or an optical fiber array and a second lateral surface not connected to the same. The substrate has a lateral surface disposed on the same side as that of the second lateral surface of the optical waveguide layer. At least a portion of the second lateral surface of the optical waveguide layer is disposed in a plane different from the lateral surface of the substrate so that an exposed area of the substrate is formed between the second lateral surface of the optical waveguide layer and the lateral surface of the substrate.