An optical device includes: a lens member including a plurality of lenses arranged such that optical axes of the lenses are substantially parallel to one another; and a light-transmitting member including: at least one light-transmitting part that is disposed to face the lens member, positioned on the optical axis of some of the plurality of lenses, and transmits light; and a light-shielding part that is provided on a surface of the light-transmitting part and blocks passage of light.