The present invention provides an optical device that is miniature, is highly sensitive and has a simplified package, and a manufacturing method thereof with high production efficiency and high reliability. The present invention is an optical device comprising: a photoelectric conversion element (50) having at least one photoelectric conversion portion (1) which is formed on a substrate (10); a sealing material (14); and a connection terminal (3). The optical device comprises an optical window which is an interface between the photoelectric conversion element (50) and an outside of the optical device; and an aperture (6) formed in the sealing material 14, and whose bottom face is the optical window. An entire face of the optical window is exposed to the outside. An optical adjustment element (13) may be formed on the interface. In this case, the interface between the optical adjustment element (13) and the outside is the optical window.