Provided are a lightwave circuit and a method of manufacturing the same. The lightwave circuit includes a first substrate having an engraved core formation groove which is formed on an upper portion of the first substrate, a core layer which is formed inside the engraved core formation groove, a BPSG bonding layer which is formed on the first substrate including the core layer, and a second substrate which is formed on the BPSG bonding layer. Accordingly, light loss and branching uniformity of the lightwave circuit are effectively improved, and the lightwave circuit is manufactured simply and inexpensively while also further improving light loss and branching uniformity of the lightwave circuit.