An optical device comprises a substrate having a first surface and a second surface being opposite the first surface a light-emitting element having a first center, installed on the second surface and a light-receiving element having a second center, installed on the first surface. At least a part of the light-emitting element is arranged at a position, overlapping the light-receiving element with respect to a plan view the light-receiving element, installed after the light-emitting element, has a bonding pad, provided at a position displaced relative to the second center towards a first direction with respect to the plan view and the first center is provided at a position displaced relative to the second center towards a second direction, being opposite the first direction DR1, with respect to the plan view.
