An optical device includes a substrate, a semiconductor chip, a resin member, and a transparent plate. The semiconductor chip is provided on the substrate, and an optically functional layer is formed in a part of a top portion of the semiconductor chip. The resin member is provided on the substrate with a top surface and an inner side surface, and has a frame shape surrounding the optically functional layer. The resin member is integrally formed from a resin material, and includes a recessed portion provided at the intersection of the top surface and the inner side surface. The transparent plate is disposed in the recessed portion. The semiconductor chip, the resin member, and the transparent plate are arranged to define airspace.