The optical device includes a photoelectric conversion block including a photoelectric conversion chip configured to include photoelectric conversion elements arranged in a matrix and a first sealing member configured to cover side faces of the photoelectric conversion chip to expose the photoelectric conversion chip and a lens block including a lens and a second sealing member configured to cover side faces of the lens to expose one surface and an other surface of the lens. In the lens block, the one surface of the lens and the second sealing member forms a recessed portion, at least a part of a bottom surface of the recessed portion being formed by the one surface of the lens, a sidewall of the recessed portion being formed by the second sealing member, and the recessed portion being arranged such that the photoelectric conversion chip exposed from the first sealing member is covered.