An optical device includes a first substrate having a first surface, a second substrate having a second surface, at least one optical waveguide, and a plurality of spacers, disposed on at least either the first surface or the second surface, that include a first portion and a second portion. The first portion of the plurality of elastic spacers is at least one elastic spacer located in a region between the first substrate and the second substrate in which the first substrate and the second substrate overlap each other as seen from an angle parallel with a direction perpendicular to the first surface. The second portion of the plurality of elastic spacers is at least one elastic spacer located in a region in which the first substrate and the second substrate do not overlap each other as seen from an angle parallel with the direction perpendicular to the first surface.